GCE 2003 June Series Report on the Examination GCE … 12,13/A level Physics pa… · · 2015-01-13June Series Report on the Examination Advanced Subsidiary – 5451 Advanced

GCE 2003

June Series

Report on the Examination

Advanced Subsidiary – 5451Advanced - 6451

GCE PhysicsSpecification A

Advanced Subsidiary

Advanced

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CONTENTS

AS Units

Page No.

PAO1 Particles, Radiation and Quantum Phenomena.........4

PAO2 Mechanics and Molecular Kinetic Theory ...................6

PHA3/P Practical Examination .....................................................8

PHA3/C Coursework .....................................................................12

PHA3/W Current Electricity and Elastic Properties of Solids..............................................................................................................14

A2 Units

Page No.

PAO4 Section A Waves, Fields and Nuclear Energy .......... 18

PAO4 Section B Waves, Fields and Nuclear Energy .......... 20

PHAP Units 5-9 Practical........................................................... 22

PHAC Units 5-9 Coursework..................................................... 26

PHA5/W – PHA9/W Section A Nuclear Instability............. 26

PHA5/W Astrophysics ................................................................. 27

PHA6/W Medical Physics........................................................... 29

PHA7/W Applied Physics............................................................ 31

PHA8/W Turning Points in Physics ......................................... 33

PHA9/W Electronics..................................................................... 34

PA10 Synoptic Unit...................................................................... 36

Mark Ranges and Award of Grades ...................................................................... 40

Physics A – Advanced Subsidiary Report on the Examination

4

Physics

Specification A

Advanced Subsidiary Examination

The Summer 2003 AS series of examinations saw one major change in the organisation of the

examinations compared with previous examinations. This year, all three written

examinations were taken consecutively within a single three hour period, each paper being of

one hour duration and limited to 50 marks, of which two were for Quality of Written

Communication.

The reduction, both in marks and time available, has had the effect of tending to remove the

easier, less significant marks in each of the three papers, thus making it harder to earn marks

than previously. Overall, the questions were slightly less accessible, but at the same time,

each paper was a fair test of the unit being examined.

The results showed that there were no significant changes in the ability of the candidate

population and in fact the performance of some candidates showed a marginal improvement

in their preparation for the examination.

Unit 1 : PA01 : Particles, Radiation and Quantum Phenomena

General Comments

The content of the questions in this paper gave all candidates opportunity to demonstrate

some knowledge of the unit specification. The photoelectric effect has, in the past, been a

topic that has not been well understood by the majority of candidates but in this examination

the examiners were pleased to see that all candidates, bar the weakest, approached this topic

successfully. It was gratifying to find that many candidates did not confuse the ejection of an

electron by the photoelectric effect with the ejection of an electron during the ionisation

process. In contrast to this, a majority of candidates appeared not to have covered the

photoelectric effect at all. Once again, about half the candidates carried out the geometrical

optical calculations successfully, but nearly all candidates found drawing even simple ray

diagrams difficult.

Question 1

This question yielded a good spread of marks, but each section presented some difficulties,

especially for weak candidates. In general, part (a) yielded good answers. In part (b) the

main difficulties encountered were converting the given information in part (iii) into correct

units and in part (iv) many candidates failed to register that four neutrons were released in the

splitting process.

Report on the Examination Advanced Subsidiary- Physics A

5

Question 2

Part (a) proved to be a good discriminator but, surprisingly, the most common error was

stating that the negative muon was not affected by the electromagnetic force.

Part (b) was answered well, apart from the use of weight instead of mass, an error which

occurred often.

The Feynman diagram in part (c) was also a good discriminator. It showed that the majority

of candidates knew which particles were involved in electron capture but that they were not

sure where to place them in the diagram.

Question 3

Answers to this short question showed that most candidates had no real idea of how a

fluorescent light tube worked and many accounts were pure guesswork. Some of the most

common errors were, stating, in part (a), that the tube was under low pressure so that it would

not break and in part (b), believing that the electrons were directed at the coating in order to

make it glow.

Question 4

Although, in general, the majority of answers were satisfactory a considerable number of

candidates had trouble in part (a) when attempting to explain the meaning of the term

threshold frequency. Very often they could not distinguish between work function and

threshold frequency.

The calculations in part (b) were carried out very well, especially when determining the value

of the work function in Joules, but only the better candidates could convert Joules to eV.

Part (c) was also tackled well and only the weaker candidates failed to draw the additional

line on the graph.

Part (d) gave candidates the opportunity to air their knowledge of the photoelectric effect but

there are still many candidates who do not appreciate the difference between changing the

intensity and changing the frequency of the incident electromagnetic radiation. However, the

written accounts indicated that more candidates this year than in previous years understood

this point.

Question 5

The calculations in part (a) and part (b) were performed successfully by about 50 % of the

candidates, but many fell at the first hurdle by trying to use the angles given in the question to

calculate the speed of light in glass, rather than equate the refractive index to the ratio of the

two speeds. A number of these candidates did however redeem themselves by calculating

part (b) successfully. The overall impression created by the examinees was that although the

relevant equations were known, they did not have the expertise to decide which equation was

appropriate to the given calculation.


6

It is difficult to understand why so many candidates find ray drawing so demanding. Only

about 10% of the candidates were awarded full marks in part (c). The errors which occurred

were not drawing equal angles for internal reflection and refracting the emergent ray towards

the normal.

Question 6

The topics in part (a), namely excitation and ionisation, have been examined before and, as

on previous occasions, candidates tried to explain the full excitation and relaxation processes

instead of simply stating that an electron is promoted up to a different energy level in the

excitation process. Ionisation was understood much better, but too many students thought the

incoming electron was captured by the atom. Although it is appreciated that temporary

negative ions or resonances occur for extremely short time periods no marks were awarded

for electron capture because it would be outside the experience of candidates.

The most common error in part (b) was not identifying the correct change in energy. Also, the

10-19

factor in the given energies was omitted in many of the calculations.

Question 7

Most candidates were aware of wave particle duality, but they sometimes lost marks through

lack of care. For example, a statement such as “an electron can behave as a wave or as a

photon” was common but did not gain any marks. In identifying the behaviour of electrons,

weaker candidates often gave an example but failed to state which type of behaviour it

represented.

In part (b) only the weaker candidates had trouble with the calculation. They either failed to

use the de Broglie equation or could not rearrange the equation to make the speed, ν, the

subject.

Unit 2 : PA02 : Mechanics and Molecular Kinetic Theory

General Comments

The performance of candidates in this unit was generally sound and a significant number

were awarded full marks. Questions 5 and 6 proved to be the most discriminating and only

the better candidates scored high marks in both these questions. Presentation was generally

good and candidates set out calculations so that there was a logical structure to their answers.

Although the rules concerning significant figures has been eased this year the number of

candidates who incurred a penalty in this examination was surprising. Five or more

significant figures were often quoted in question 4(b) and the impression given was that

candidates were more reluctant to round down their answers than had been the case in

previous years.


7

Question 1

This question was well answered and candidates were consistently able to extract and use

appropriate formulae in their calculations. In part (a), a minority of candidates used 293 K as

the change in temperature rather than 20 K, but this was less prevalent than in previous years.

There were problems with stating the appropriate assumptions in part (b). Many candidates

stated incorrectly that no heat was lost to the surroundings.

Question 2

Candidates found this question reasonably familiar and had more success, especially in part

(a), than had been the case with similar questions in the past. In part (b), more candidates

than previously seemed familiar with light gates and data loggers and were able to describe

clearly the use of these devices. A minority of candidates had obviously studied a similar

question in the January paper, a question which had required candidates to describe how the

speed was measured after a collision. These candidates then tried to answer this question in

the same way with the result that their answers were generally inappropriate.

Part (c) caused more problems than anticipated as many candidates misinterpreted the

question and explained why the speed of the trolley might vary and not how.

Question 3

The application of Newton’s laws to terminal velocity has been assessed before and

candidates are improving at expressing themselves when answering this type of question.

Fewer candidates now make the mistake of assuming air resistance reduces the speed as

opposed to reducing the acceleration. Confusing acceleration with force is also less common

and although statements such as “Air resistance equals the acceleration due to gravity” did

occur in many scripts, they were certainly less frequent than previous. The commonest error

which occurred was applying Newton’s third law incorrectly and identifying air resistance as

an equal and opposite reaction to weight. Part (ii) produced some interesting responses and

many candidates seemed unaware that gravitational acceleration is independent of mass.

Question 4

Most candidates found this question quite accessible although weaker candidates were

confused by the concept of resolving a force into two perpendicular components. A

surprising number of candidates gave incorrect responses to part (a) but were completely at

ease with part (b), scoring maximum marks. There were several approaches, correctly used,

to deduce the tension in the cable. Some of these methods were extremely complicated but

eventually generated the correct answer. This question produced the greatest number of

significant figure errors.


8

Question 5

Part (a) discriminated very well and although most candidates scored some marks, only the

best were awarded the maximum. The two sections least well done were part (iii) which

asked what the area under the line AB represented and part (v) which asked why the speed at

C was less than the speed at B. In answering part (v) a significant proportion of candidates

did not realise that the ball rebounded from the floor at C.

Part (b) also produced a variation of marks. Most candidates completed part (i) but found the

other parts of the question more difficult. There was considerable confusion over signs and

initial and final velocities in part (ii). This confusion was carried over into part (iii) and most

candidates made no allowance for the change in direction of momentum but simply

subtracted the magnitudes of the initial and final momenta. As in the past, the unit for

momentum caused problems and penalising a unit error at this point was quite common.

Question 6

This question also gave good discrimination. In part (a) the better candidates made very few

errors and scored high marks but the less able candidates found it more difficult and were

unable to come up with three assumptions of the kinetic theory.

The calculation in part (b) caused problems and even candidates who selected the correct

expression had difficulties. The commonest of these was failing to convert the temperature to

Kelvin.

Part (c) was answered correctly by only the best candidates and although many did identify

that molecular mass was important, they could not quite explain why.

Unit 3 : PHA3/P : Practical

General Comments

Both questions discriminated successfully with practically all of the 30-mark range, including

full marks, being utilised. Question 1, which assessed AO3a, worked particularly well with

significant percentages of candidates at each mark. The distribution of marks for question 2

was wider than seen before, possibly due to the more difficult nature of the exercise set, and

produced better discrimination at AO3b and AO3c than previous examinations. Although

some candidates continue to struggle with the part of question 2 which addresses AO3d,

many were successful.

The relative lack of success of many candidates in AO3a and AO3d highlighted the

inefficient way that some candidates extract information through reading, and also their

limited ability to express ideas clearly when writing in continuous prose. In question 1

several wrote that they would measure the area of the cake-case using a ruler and in question

2 it was common to find candidates describing how the magnitude of the readings would

change when the experiment was repeated with the block rotated, whereas the question asked


9

how the range of these readings would be affected. The most costly error was the use of (θ1 –

θ2) instead of sin (θ1 – θ2) along the horizontal axis of the graph.

The length of answers for question 1 was more modest than seen in previous examinations

and generally less use was made of supplementary answer sheets. This may be due, in part, to

the more demanding nature of question 2, but nearly all candidates appeared to manage their

time effectively. Answers generally gave some details of measurements, strategy and, more

occasionally, control factors and procedures to overcome difficulties involved in the plan.

Sketches and diagrams often contributed to these plans but some candidates seem obsessive

about using the available space to the full and this inevitably leads to repetition or even

contradictory answers.

Most candidates demonstrated a reasonable understanding of the physical principles involved

in the cake-case problem but very often it was not made clear that terminal velocity had been

reached before measurements on the motion were to take place. Many candidates understood

the need to repeat the experiment by either varying the weight and/or size of the cake-case so

as to increase the amount of evidence on which to base their determination of the shape

factor. Marks for procedures and difficulties were often withheld because the procedures

given failed to refer explicitly to the measurements being done, e.g. statements such as “find

the velocity again and take averages” could as easily refer to the calculation process as to the

timing of the transit of the cake-case.

Question 2 posed a sterner test for candidates than those set in recent examinations. The

experiment relied on careful work to accurately find the displacement of the light ray. Many

graphs contained considerable scatter although it was generally possible for an adequate best-

fit line to lead to a successful conclusion.

Some candidates scored more on question 1 than on question 2 but just as many scored

heavily on question 2 and made little or no progress on the planning exercise. As a whole, the

paper showed that relatively few candidates could score heavily across all the assessment

objectives but this discriminated strongly in favour of the better experimental physicists

Question 1

Candidates were required to describe a method of determining the shape factor, f, of a paper

cake-case of cross-sectional area A, falling with terminal velocity, v, the drag, D, being given

by D = fρAν2, ρ being the (known) density of air.

Most candidates knew some or all of the relevant physics but there seemed to be some

confusion whether Newton’s first or third law could be applied to the situation. Others tried

to bring in the second law, quoting Fmv

t= ∆

∆( )

as the means to determine the drag.

Significant numbers of candidates made the assumption that the cake-case, when dropped,

would instantaneously reach terminal velocity rather than ‘quickly reach terminal velocity’ as

the question suggested. Failure to take account of the acceleration of the cake-case before

reaching terminal velocity prevented the award of marks, which otherwise would have been

given for use of a stopwatch to measure the transit time and a ruler to find the vertical

distance covered by the cake-case.


10

Many candidates referred to the use of one or two light gates in their plans. For credit to be

given, examiners needed to see that these were used in conjunction with data logging systems

and that the candidate was clear that the gates acted simply as sensors. For single gate

methods, candidates were expected to mention that the obscuration height of the cake-case

should be measured. Many candidates understood that when terminal velocity had been

reached, the drag force was equal to the weight of the cake-case and credit was given for use

of a balance to determine the mass, and hence the weight, of the cake-case. Marks were

forfeited by the inaccurate use of terminology: ‘scales’ were not accepted for ‘balance’, nor

was ‘timer’ accepted for ‘stopwatch’ or ‘stopclock’. The majority of candidates explained

that a ruler could be used to find the diameter of the cake-case but few thought it necessary to

repeat this measurement in several directions and then average, in order to reduce the

uncertainty in the result.

Nearly all the candidates explained how the terminal velocity would be calculated using

vertical distance and transit time. Exceptions were those who failed to appreciate the

changing pattern of motion during the descent and described the use of equations for

uniformly accelerated motion. The correct explanation of how the diameter could be used to

calculate the area of the cake-case was nearly universal.

Statements that the drag was equal to the weight once the terminal velocity had been reached

were less widespread: some candidates decided that drag was an unknown that could be

eliminated by repeating the experiment at some different terminal velocity and then using

simultaneous equations.

The idea that a satisfactory result for the shape factor could be obtained from a single set of

measurements of velocity, drag and area was not accepted, but many candidates picked up the

hint given in the question and wrote that they would repeat the experiment, stacking

additional cases together to increase the weight. Relatively few took the further step and

explained how a graphical method, e.g. plotting D against ρAv2, and determining the gradient,

could produce a more reliable answer for the shape factor.

There was very little the candidates could suggest about relevant control measures, other than

the elimination of draughts ,but surprisingly few did this.

Credit was given when candidates wrote about procedures that would reduce the uncertainty

in measurements, although no credit was given for putting multiple cake-cases on the balance

to determine the average mass. Among the stranger suggestions seen was that the experiment

would run better if air resistance could be removed altogether by performing the experiment

in a vacuum chamber. Other answers that earned credit included increasing the vertical

distance over which timing took place, avoidance of parallax error when starting or stopping

the stopwatch and the use of a set square to ensure that the ruler used to determine the transit

distance was vertical.

In the majority of cases where a procedure mark was awarded the candidate simply said they

would repeat the timing and average the result (or check for the presence of anomalous

results). When candidates did not specifically refer to a procedure to overcome errors in

measurement, as opposed to calculation, it was difficult for the examiners to give credit. An

additional mark was given if the specific difficulty that the procedure sought to overcome

was identified.


11

Question 2

Candidates were required to investigate the deviation of a light ray passing in to and out of

the opposite sides of a rectangular transparent block.

The width of the block was almost universally recorded accurately although a few candidates

gave centimetres as the unit when they meant millimetres. A surprising number of candidates

took no notice of the instruction that the initial measurements of θ1 and θ2 should be chosen

so that (θ1 − θ2) was at least 25°, while others chose to record the angles in a way that was

inconsistent with the data in the main table. It was expected that if any angular or linear

reading was interpolated to a half scale division then all the data should be recorded in a

similar fashion, e.g. 12.5, 14.0, 17.5 etc. Readings given to less than half a scale division

were not accepted.

The majority of candidates produced a value for the refractive index of the block that fell

within the expected range of 1.35 to 1.65 and recorded the result without a unit, as required.

Marks were awarded for tabulating the raw data and for tabulating the derived data. The most

common error seen was when (θ1 – θ2) was recorded instead of sin (θ1 – θ2). The omission of

a unit for s cos θ2 in the table headings was not penalised although the omission was not

tolerated on the labelling of the graph axis. For those candidates who chose to omit units for

the s and θ labels in the table headings of the raw data, it was expected that every data item

should have a unit attached: any omission resulted in the loss of one tabulation mark.

Most candidates supplied five data sets as the question required and very few used too

restricted a range (it was expected that the s data should span at least 10 mm). The main area

of concern was the consistency in tabulating results as outlined above. Consistency was also

an issue for the derived data sets: these should have been either to 3 or 4 significant figures,

but many instances were seen in which the sin (θ1 – θ2)

data were given to only 2 significant figures, a factor that contributed to much of the scatter

produced on the graphs.

The quality of the work done was judged by this scatter: if four of the five plotted points fell

within 2 mm of the line, a mark was awarded, but it was common to find that this mark and

that for significant figures were usually withheld.

The general standard of the graphical work showed that many candidates appreciated the

need to mark axes appropriately, although scaling marks were frequently lost due to the

inclusion of an origin and the resulting compression of the horizontal scale, or for the use of

difficult scales e.g. use of 3 × 2 mm grid lines to represent 10 mm on the vertical axis.

Candidates should understand that the accuracy with which they plot points on the graph is

checked and it was not uncommon to find evidence of incorrect plotting, either through

carelessness or design on the part of the candidate.

Gradient calculations were done in most cases with sufficiently large y and x steps, except

where compressed graph scales had made the line too steep or too shallow, but the numerical

result often corresponded well enough with that recorded earlier for the width of the block so

that full credit could be given.


12

The standard of answers seen for the concluding questions, assessing AO3d, varied

considerably. In part (e)(i), most candidates showed that they appreciated that the magnitude

of the measurement being made influenced the uncertainty in the result. However many

candidates phrased their answer so that it appeared they were discussing the angle of

deviation, (θ1 – θ2), rather than the angle of incidence, θ1, and the angle of refraction, θ2.

In part (e)(ii), relatively few candidates could make two sensible points concerning

procedures to reduce the uncertainty in s: credit was given if candidates said they measured

the distance in more than one place (to check for consistency) or if they said that they

checked that the distance measured was perpendicular to the emergent light ray by using a

protractor or set square. Some candidates interpreted the question as requiring an explanation

of how the direction of the emergent ray had been marked accurately.

In part (e)(iii) many candidates appreciated that if the experiment was repeated with light

travelling in to and out of the block through the shorter sides, the point would quickly be

reached where the internal ray could not pass through the required surface, but the ambiguous

nature of many answers prevented credit being given. Candidates simply had to say that, in

each case the range of readings available would be reduced, but far too many wrote about the

size rather than the range of readings or did not make a clear comparison between the

situation described and the experiment they had just performed.

Unit 3 : PHA3/C : Coursework

Most Centres completed the administration procedures correctly and copies of Centre

Marksheets and samples of the candidates work reached moderators by the prescribed

deadline. In a few cases, however, there was some confusion as to which copies of the

Centre Marksheet should be sent to the moderator. In small Centres of less than 20

candidates, only the pink copy should be sent, together with the candidates work; the yellow

copy should be retained by the Centre. For larger Centres, both pink and yellow copies of the

Centre Marksheet should be sent to the moderator. The yellow copy will be returned,

specifying the samples to be sent to the moderator.

Whilst, in general, the quality of annotation was good, a small but significant proportion of

Centres failed to adequately annotate the work submitted. It should be noted that every

marking point must be annotated at the precise point where the mark was awarded. The

annotation should be written in the format ‘A4b’, ‘B6a’, etc. referring to the appropriate

marking point. Written comments are also helpful, especially in clarifying why a particular

‘marginal’ point has been awarded. The use of a suitable marking grid to record the

individual marking points is also strongly recommended. This makes it much easier to

interpret the hierarchical scheme and determine the total mark for each skill. A further

confusion arose with a small number of Centres, who apparently used the GCSE skill letters

P, O, A and E rather than A, B, C and D.

As in previous years a significant number of adjustments were made to the marks submitted

by Centres. Almost all Centres applied the hierarchical scheme correctly. Mark adjustments

were mainly due to misinterpretation of specific points in the assessment criteria. This is

explained in more detail below. Due to the hierarchical nature of the scheme however, one

error in interpretation of the criteria can cause a significant adjustment to the overall mark,


13

e.g. a candidate who, in the opinion of the moderator, has failed to achieve A4c (fully

labelled diagram) will be limited to a maximum of 3 marks for planning. If this mark had

been awarded by the centre, then it could result in a mark change from 8 to 3.

In most cases the investigations used were appropriate, allowing candidates access to the full

range of assessment criteria. Experiments on measurement of resistivity and emf/internal

resistance were again very popular and were successful in allowing a full range of marks to

be achieved by candidates. A small number of centres presented investigations which were

too simple. This limits the total mark which can be achieved on some skill areas e.g. Hooke’s

law for a simple spring.

As in previous examinations a small proportion of candidates made use of ICT. Whilst

appropriate use of ICT is to be encouraged as part of investigative science, many candidates

were penalised due to graphs and results tables which did not meet the assessment criteria.

Where spreadsheets were used for tabulated data, inappropriate numbers of significant figures

were often quoted. This was mainly due to ‘dropping’ of the last zero. Candidates should be

aware of this and make suitable corrections.

Graphs drawn by ICT software must meet exactly the same criteria as hand drawn graphs.

They should produce a graph which covers a full side of A4 paper, with a suitable title and

fully labelled axes. Data points should be plotted as points or crosses and not shapes, such as

large squares or diamonds, which make precise location of the plotted point more difficult.

The line of best fit should be drawn, taking account of any anomalous points. The graph

should have suitable gridlines so that accurate readings for gradients or intercepts can be

recorded. A suitably large triangle for measurement of gradient must also be shown.

The following advice, addresses issues raised by moderators on the marking of specific skills.

Many of these points were also discussed in the recent series of Teacher’s Support Meetings

held last autumn.

In skill A there were still a few cases of candidates failing to mention a consideration of

safety issues, effectively limiting their mark to a maximum of 1. To achieve A4c, diagrams

must be two dimensional, fully labelled and dimensions being measured must be clearly

indicated. This point was often misinterpreted by centres, and frequently caused a significant

adjustment to the marks awarded. To achieve A6d, full instrument specification is required;

for electric meters this requires both range and sensitivity.

In skill B, some candidates failed to take enough readings with appropriate repeats to achieve

B4c. In an experiment to investigate the variation of resistance with the length of a wire, it

would be expected that candidates take at least 7 or more different lengths, with repeat

readings for the resistance at each length. Some centres, where candidates had only done 5 or

6 different readings, awarded this mark incorrectly.

Quoting results to an inappropriate number of significant figures was the main cause for

concern in skill B. This usually occurred where a length measured to the nearest mm was

quoted only to the nearest cm, e.g. 0.20 m rather than 0.200 m. This often results in a mark

adjustment from 8 to 5 on this skill.

In B6d, candidates must clearly identify the significant source(s) of error which occurred in

their experiment. Although they might have suggested a particular source in the planning


14

stage, a further statement would be required after results have been taken in order to confirm

whether or not this is still considered to be the most significant source of error.

To achieve C4c in skill C, an appropriate scale must be used so that the plotted points occupy

more than half the length of each axis. If this makes it impossible to read a particular

intercept directly, a suitable calculation should be done instead. Some centres awarded C4c

for graphs with no titles and where the plotted points occupied less than a quarter of the area

of the paper. This caused significant adjustment to the marks awarded, effectively limiting

the mark for skill C to a maximum of 3.

In skill D the majority of candidates scored less than in the other skill areas. Many

candidates failed to achieve all four marking points in D2, thereby effectively limiting their

mark to a maximum of 1 for this skill. In particular, for D2b a simple statement about

discrepancies or anomalous results is required. For D2c, candidates must state whether there

is much variation in their repeated results, indicating the level of uncertainty in the data. In

D4b, candidates frequently calculated errors based on instrument sensitivity only.

Where possible, the error estimate should be based on the spread of repeated results, e.g. in

an experiment to investigate the variation of resistance with length of wire, the error in length

might reasonably be based on the accuracy of the rule (± 1 mm). The error in resistance

however, should be taken from the spread of repeated readings and not from the sensitivity of

the meters used. In D6a, a large proportion of candidates are unsure of the difference

between random and systematic errors.

Unit 3: PHA3/W: Current Electricity and Elastic Properties of Solids

General Comments

The paper was of a similar nature to last Summer’s paper, but being of 1 hour duration

(compared with 1 hour 15 minutes last year) there were fewer questions and one topic less

being examined. The paper worked satisfactorily and all marking points were gained. A few

candidates gained the maximum mark of 50 and very few candidates failed to score a

reasonable number of marks. The first three questions involved electrical calculations and

consequently required units to be quoted regularly and it was satisfying to see that

comparatively few candidates omitted units or gave the wrong one. Significant figure errors

were not so much in evidence as last summer because of the new ruling that two, three or

four figures were acceptable. However a worrying number of candidates rounded down to

one figure mid-way through a calculation and consequently rendered the remaining

calculation meaningless in terms of numerical values. A frequent example of this occurred in

question 3. A similar rounding down in the final calculation would incur a penalty. The

Quality of Written Communication was of a good standard and very few candidates failed to

gain at least one mark.

Question 1

In this example of calculating equivalent resistance, the same resistor network was used

twice, the equivalent resistance being calculated between different terminals. The majority of


15

candidates had no difficulty with the calculations, but it was worrying to find many answers

where the candidates had attempted a solution, not by calculation, but with phrases such as

“electricity takes the path of least resistance and therefore the effective resistance (in part (b))

is 50 Ω.”

It was surprising to find that a significant number of candidates obtained the correct result in

part (b) but failed on part (a), since part (b) was deemed to be the most difficult of the two.

Considerable arithmetical difficulty was encountered by many candidates with the reciprocal

of the resistance when calculating the resistance of parallel resistors.

Question 2

This question worked well and many candidates gained full marks. The majority of the other

candidates only failed to gain maximum marks because of a unit error or significant figure

error. Disappointingly, many answers were expressed as a fraction. It should be noted that

this practice is not acceptable and the first answer expressed as a fraction was treated as a

significant figure error.

In part (i) the error which occurred most frequently was ignoring the internal resistance of the

battery. The correct answer was 0.19 A, to two significant figures, but many candidates

rounded this down to 0.2 A, which apart from incurring a penalty, also, when carried forward

to part (ii), gave a voltage across the resistors of 12 V. This implied that there was no voltage

developed across the internal resistance of the battery. Although many candidates produced

such an answer no one noted that such a situation was not possible. Many answers to part

(ii), when carrying forward an incorrect value of the current from part (i), gave an answer

well in excess of 12 V. Again this did nor seem to worry the candidates.

In part (iii) many candidates made the error of calculating the power dissipated in the total

external resistance instead of in resistor A alone. The unit of power was usually correct as

was the unit of energy in part (iv). Many candidates arrived at the correct answer in part (iv).

Consequential errors were carried forward throughout the whole question. This gave many

candidates the chance to gain some marks even if their initial calculation and subsequent

answer was incorrect.

Question 3

This question involved the analysis of a relatively difficult circuit, which included two lamps

and two resistors. The question however, was so structured that the majority of candidates

were able to work through and gain full marks. Others, unfortunately, although making a

reasonable attempt, failed to gain many marks. In part (a), the majority of candidates

calculated the correct value of the currents passing through each lamp.

In part (b), obtaining the correct answers to parts (i) and (ii) depended to a large extent on

realising that the reading on the voltmeter equalled the voltage across lamp X. Many

candidates missed this point, but were still able to gain some marks. In part (ii) the error that

was committed regularly was determining the resistance of lamp Y instead of the resistance

of resistor R2. But at least, most candidates realised that the same current passed through

lamp Y and R2. Answers to parts (iii) and (iv) used the answer to part (a) as a starting point,


16

but many candidates failed to realise that the current through R1 was the sum of the current

through the two lamps. Considerable guesswork took over at this stage and although most of

it was wrong, candidates could still get a mark for part (v) by using the answers obtained to

parts(iii) and (iv).

Question 4

Question 4 gave candidates the opportunity to describe an experiment and also gain the

‘quality of written communication’ marks. Most of the descriptions were satisfactory, but

examiners were disappointed by the large number of candidates failing to explain clearly that

measurements of voltage and current were repeated for different settings of the variable

resistor. Examiners had to read between the lines to see if the candidates were in fact saying

this. It is difficult to imaging a description of a simpler experiment being asked and it was

sad to find that many candidates did not gain high marks because of their inability to express

themselves clearly.

The circuit was usually drawn correctly, using either a variable resistor or a potentiometer as

the extra piece of apparatus. The potentiometer caused some consequential problems

however, because the ammeter would then be inserted in the part of the circuit leading into

the potentiometer and not in series with the wire.

Many candidates obviously did not read the question thoroughly since switches were missing

and the actual wire whose resistance was required, was frequently omitted. Several

candidates used a variable source instead of a variable resistor. This was not accepted. The

other common error which occurred on far too many occasions was misreading the question

completely and embarking on an experiment to determine the resistance of a variable length

of wire and hence the resistivity of the material. In such answers, marks were given for the

circuit, but none for the description.

The majority of candidates knew how to obtain the resistance from the observed values using

either a graphical method or a calculation of R = V/I and then taking the mean. Several

candidates took the mean of all the voltage measurements and the mean of all the current

measurements and thus obtained one value of the resistance. This was considered to be poor

practice as a method of determining the value of resistance.

The calculation in part (b) was usually correct and many candidates gained full marks. One

error which occurred frequently and which incurred a penalty, was not treating the rms

voltage as the working voltage, but converting it to peak voltage. The other error was

incorrect use of the equation relating resistivity and resistance.

Question 5

Examiners were pleased to find that part (a) was answered satisfactorily and that candidates

not only chose the correct wire but were very often able to provide the correct reason for

doing so. Many candidates gained full marks, while a large number only lost one or two

marks. Part (i) was usually correct, although reasons such as ’the graph is a straight line’

were not accepted. A ‘constant gradient’ was accepted but few candidates gave this as a

reason, most giving the proportionality of the quantities involved. In part (ii) answers such as


17

‘Y broke before X’ was not accepted. Examiners were looking for a reason in terms of lower

breaking stress.

Answers to part (iii) were not so good and candidates who did not know the correct answer

attempted an answer in terms of the gradients of the curves or the bending of curve Y as the

tensile strain increased. Part (iv) gave the most trouble. Many candidates again tried an

explanation in terms of the gradient, but a significant number followed the correct track and

gave a reason in terms of the area under such a graph. Unfortunately the majority of these

candidates referred to the area under the whole curve, whereas it should have been the area

under the curve at a given tensile stress. Surprisingly, many candidates, even when using a

given stress, gave the area under X as being greater than that under Y.

The final calculation in part (b) did not cause too much difficulty and, provided the initial

equation for the Young modulus was correct, candidates produced a correct answer with

correct units. One common error which again arose from not reading the question

thoroughly, was using the extended length of the elastic cord as the extension. Converting

the cross-sectional area of the cord from mm2 to m

2 caused some problems, but this error was

carried forward after the initial penalty had been imposed. The calculation in part (ii) was

also done well by those who knew the expression for the energy stored, or were aware that it

was given in the data sheet. Some answers, resulting from a carry forward of an incorrect

force in part (i) gave energies amounting to several million joules. This attracted no

comment.

Physics A – Advanced Report on the Examination

18

Advanced Examination

The summer 2003 series of examinations was the third series for all A2 papers to be

examined. The other two were Summer 2002 and January 2003. The examination is now

well established and the only change from last year was that the Quality of Written

Communication marks were incorporated into the total for a paper, instead of being

additional to the total.

The performance of candidates at the upper end of the ability range was only marginally

down on last year. The examiners felt, however, that there was a long tail to the distribution

curve and many of the weaker candidates showed evidence of lack of preparation for an A-

level examination.

Unit 4 : PA04 : Section A : Objective Test Questions

The keys to the objective test questions were:

1-A; 2-B; 3-A; 4-B; 5-A; 6-B; 7-A; 8-A; 9-D; 10-C; 11-C; 12-D; 13-A; 14-C; 15-D.

General Comments

The facility of a question is a measure of all candidates attempting a question who choose the

correct option. The mean facility of this paper was 60%, compared to 57% in January 2003

and 61% in June 2002. The facility for individual questions ranged from 83% for question 6

to 47% for questions 3 and 9.

The point biserial index (or discrimination index) of a question is a measure of how well the

question discriminates between the most able and the least able candidates. The mean point

biserial for this paper was 0.44, closely similar to the values of 0.41 and 0.44 respectively in

the January 2003 and June 2002 tests.

Questions 6, 10, 14 and 15 proved to be easy, with facilities over 65%, whilst none of the

questions had facilities less than 35% and could thus be considered difficult. Two questions

had appeared in earlier Advanced Supplementary papers and in both of them candidates’

performance in June 2003 was markedly better than that on the earlier occasions. One

question had been used in the 1997 Advanced Level examination and in this the performance

of the June 2003 candidates was significantly worse than in 1997.

Statistical analysis of the results has shown this test to be of comparable demand to that set in

June 2002.

Question 1 tested candidates’ understanding of the acceleration of a particle moving with

simple harmonic motion. Over half of the candidates gave the correct response, but one in

five of them thought that the acceleration was greatest at zero displacement.

Question 2 involved a calculation of the maximum kinetic energy of a particle moving in

SHM. The examination facility of this question was 57%, much better than the pre-

Report on the Examination Advanced - Physics A

19

examination facility of 38%. Incorrect responses were fairly evenly split between the three

remaining distractors.

Question 3 was one of the more demanding questions in this paper. No doubt the algebra

required to think through what happens when the length of a pendulum is changed was the

main obstacle to the progress of weaker candidates. The examination facility was 47%.

However the question was one of the best discriminators in this paper, with a discrimination

index of 0.52. 41% of the candidates chose distractor C, suggesting either that they did not

understand that

T ∝ l1/2

, or that they were guessing that half the length would give half the period.

Question 4 was answered correctly by 58% of the candidates. Lack of understanding of

radian measure when considering phase difference probably accounted for 27% of the

candidates choosing distractor D (3π/2), rather than π/2.

Three-fifths of the candidates gave the correct response in Question 5, previously an AS

question, where knowledge of c = f λ was combined with the need to comprehend the

meaning of the frequency of a wave. Mistakes with the arithmetic probably accounted for

distractor D being chosen by almost 20% of the candidates.

Questions on double-source interference experiments have appeared frequently in these

objective tests. The 2003 candidates appeared to have been well rehearsed for Question 6,

which, with a facility of 83%, was the easiest in this paper. It still had a very satisfactory

discrimination index of 0.46.

Question 7 was a two-stage calculation on a diffraction grating. Slightly fewer than half of

the candidates could cope with this. Wrong responses were almost evenly divided between

distractors B and C, with very few choosing D.

Energy stored by a capacitor was the subject tested in Question 8, which had been used

before in an Advanced level examination. In June 2003 the examination facility was 56%, as

opposed to 67% when it was used before. The discrimination index was very similar on both

occasions.

Question 9 required candidates to be familiar with capacitor discharge and the concept of

time constant. Almost half of them chose the correct response, but 27% of them thought that

the remaining charge would be Q0 e2 after a time of 2RC. Perhaps this was caused by

misreading (Q0 e2) as (Q0 /e

2).

Most candidates were able to deal competently with Question 10, where almost four-fifths of

them obtained the correct value for the angular speed of the roundabout.

Understanding of the forces involved in circular motion was a prerequisite for Question 11.

Although the examination facility of this question was 62%, the discrimination index (0.30)

was the poorest of any question on this paper (however this is better than when the question

was last used in an old AS paper). For teaching purposes it is important to note that nearly

20% of the candidates considered that the force keeping the mass at rest relative to the disc is

a frictional force directed along a tangent to the circular path.


20

Question 12 demanded an understanding of the inverse square aspect of Coulomb’s law.

Like Question 3, it showed that many candidates do not understand proportion when the

relationship is not direct. 49% selected the correct response, but over 25% settled for

distractor B (F /9r) instead of D (F /9).

In Question 13 three-fifths of the candidates appreciated that the electric field strength is

constant between parallel charged plates. Over 20% of them chose distractor C, where the

field strength is shown as decreasing to a minimum value midway between the plates.

Questions 14 and 15, on nuclear fission and artificial transmutation respectively, were

relatively straightforward tests of knowledge. Each produced an examination facility of just

over 70%. The most popular distractor in question 14 was D, where the candidates presumed

that control rods work by slowing neutrons down rather than by absorbing them.

Unit 4 : PA04 : Section B : Waves, Fields and Nuclear Energy

General Comments

Some good, exceptionally well written scripts were seen from candidates who had come to

terms with the breadth and depth of the content of the Unit 4 specification. The four

questions all proved to be accessible, and they gave good coverage of the work involved.

Excellent answers to all of them were presented in some scripts. However, many candidates

had considerable difficulty in making progress with any of the questions. A total mark of 10

or less (out of 30) for this section was not uncommon. Whether this is because candidates

were mentally exhausted by their efforts at the fifteen objective questions in Section A, or did

not realise that Section B accounts for one half of the total mark for Unit 4, or were simply

inadequately prepared, is a matter for conjecture.

The mathematical synthesis required in Question 2, part (b) and Question 3, part (b) was

beyond the abilities of a large proportion of the candidates. This contrasted with the

arithmetic of Question 4, part (b)(i), which was almost universally correct.

Most candidates are now making greater efforts to address the quality of their writing than

was evident in 2002. In those sections where QWC is being assessed they are taking much

more care to write answers in properly constructed sentences. Yet in some scripts there was a

tendency to write well in Question 1, part (a), but to allow matters to go to pieces in Question

4, part (a); this made it seem as though QWC was being overlooked by some candidates in

the later stages of the examination. The use of correct technical terminology is part of the

QWC assessment, and examiners were not prepared to award two marks for QWC to

candidates who referred to “a maxima”, “a minima”, “a nuclei”, or “nucleuses”.

Apart from Question 3, part (a), where magnetic units were specifically targeted, unit

penalties were fairly rare in this paper. Significant figure penalties were imposed in Question

4, part (b)(ii) when the final answer was quoted to more than four significant figures.


21

Question 1

In part (a) it was evident from their responses that many candidates had no real idea about

what was happening to produce the maxima and minima. Where the formation of a

stationary wave had been recognised, the mark scheme gave ample reward to candidates who

mentioned interference effects between the transmitted and reflected waves. Most candidates

recognised this as an interference phenomenon, but many of them attributed the effect to the

diffraction and overlap of two transmitted waves. It was often stated that “the fringes” (or

“bright patches”) could be detected only at the metal plate, in a misunderstanding of Young’s

double slit experiment. Some candidates even blamed the effect on detecting the crests and

troughs of a single progressive wave, whilst references to longitudinal waves were also

encountered. Examiners could not award any marks for part (a) when the confusion was so

extensive as in these examples.

Ignorance of the fact that the separation of the nodes in a standing wave is λ/2 was the usual

cause of the loss of the mark for part (b)(i). Candidates who got this wrong were still allowed

to gain both of the remaining marks in part (b)(ii).

Question 2

Two appropriate features of a geo-synchronous orbit were usually given by the candidates in

part (a), but the marks for them were often the last that could be awarded in this question.

The required radius in part (b)(i) came readily to the candidates who correctly equated the

gravitational force on the satellite with mω2r, applied T = 2π/ω, and completed the

calculation by substituting T = 24 hours and the values given in the question. Other

candidates commonly presented a tangled mass of unrelated algebra in part (b)(i), from which

the examiners could rescue nothing worthy of credit.

In part (b)(ii) an incredible proportion of the candidates assumed that it was possible to

calculate the increase in the potential energy by the use of mg∆h, in spite of the fact that the

satellite had be raised vertically through almost 36,000 km. These attempts gained no marks.

Other efforts started promisingly by the use of V = −GM / r, but made the crucial error of

using (4.23 × 107 – 6.4 × 10

6) as r in the denominator. Some credit was available to

candidates who made progress with a partial solution that proceeded along the correct lines,

such as evaluating the gravitational potential at a point in the orbit of the satellite. Confusion

between the mass of the Earth and the mass of the satellite was common when doing this.

Question 3

The lack of familiarity of candidates with the units of electromagnetic quantities continues to

be a cause for concern. All four units had to be correct for the first mark in part (a). It might

have been anticipated that candidates would make an incorrect choice for B, such as the

regularly encountered Wb. The many candidates who could not identify the SI unit of force

(sometimes N m-1

or J m-1

were given) came as a greater surprise. The most common error in

the second aspect of part (a) was to state that the force must be perpendicular to the magnetic

field, although some candidates confused the question with electromagnetic induction and

thought that the conductor had to be moving.


22

A large number of clear and succinct solutions were seen in the answers to part (b), although

many other candidates were stumped by the need to combine ideas about magnetic force and

weight. Equating mass with magnetic force was regarded as a serious error of physics for

which no further marks could be given. The final part of the question required the accurate

application of Fleming’s left-hand rule; this defeated far more candidates than it ought to

have done.

Question 4

Candidates familiar with the principles of nuclear fusion could score all three marks in part

(a) without trouble. The main weaknesses in many scripts were caused by a tendency to

write generally about the mass difference of a nucleus rather than specifically about the

increase in mass difference brought about by the fusion of two light nuclei. Arguments

phrased in terms of the increase in binding energy per nucleon conveyed the most convincing

answers. When addressing the second half of the sentence, a large proportion of the

candidates had their attention distracted by concentrating on the need for a high temperature.

They would have been better advised to focus on the basic physical principle of electrostatic

repulsion between two positively charged nuclei. There was also some confusion with effects

attributed to the strong nuclear force.

In part (b) the calculation of mass difference caused few problems, but the conversion of

units in part (b)(ii) was a bigger hurdle. The main errors were forgetting that

1 MeV is 106

eV (which is 1.6 × 10-13

J), and attempting to convert from eV to J by dividing

by e instead of multiplying by e.

Units 5 - 9 : PHAP : Practical

General Comments

The marks obtained by the candidates for this paper contrast sharply with those obtained in

Spring 2003. Although the standard deviation for each examination is very similar the

distribution for the summer examination has shifted three marks towards the upper end of the

range. This impetus for this shift seems to have been provided by the two questions in equal

measure.

In the Spring paper, 30% could make no progress at all with question 1 (AO3a), but in the

Summer version very few failed to score and the fraction obtaining the maximum (8 marks)

more than doubled. Candidates tend to find the measurement marks to be more accessible

than the control marks: in the latest paper three measurement and one control mark were

available whereas in January two were available in each category. The impression was gained

that the candidates made better progress at defining a suitable strategy this time although

most continue to find the procedure/difficulty marks hard to come by.

The second question required candidates to time a transient event (the time for a voltmeter

reading to fall by 50%) whereas in the Spring equivalent, candidates timed the oscillations of

a compound pendulum. The data generated by the latest experiment produced a clear straight

line and this seemed to fit the graph paper conveniently, alleviating problems with choosing a


23

suitable scale for each axis, while the pendulum experiment generated a gentle curve, a fact

that many candidates failed to spot.

But while marks came more easily in the parts assessing AO3a, b and c, candidates continue

to find the marks for AO3d elusive. The question exposed a weakness on the part of many

candidates in applying their knowledge of circuit theory to a situation when a voltmeter with

different characteristics was used.

The standard of presentation seen in the scripts varied enormously, some verging on

illegibility; candidates cannot complain if the examiner is unable to give full credit for their

work in such cases. Candidates were prompted to use a diagram with their answer to

question 1 but these often failed to shed much light on the solution offered to the problem

posed in the question. In many cases details were given that cast the candidates

understanding of circuit theory in a very poor light. Graphical work, for the reasons given

earlier, was rather better than that seen in recent examinations although the inaccurate or poor

marking of points was still prevalent in the work of weaker candidates.

Candidates at this level are generally reliable at performing routine mathematical operations

but some should take more care in the way that final answers are presented: many instances

were seen in 2d(ii) where the evaluation of G

T0 was given to too many significant figures

and/or without an appropriate unit.

The use of supplementary sheets, especially in question 1, is a diminishing problem and one

which might die out completely once candidates understand that there is no credit to be

gained from providing repetitive answers or for explaining what they assume the physics of

the situations involved in the problem to be.

Question 1

Candidates were required to devise a method of comparing the decay in amplitude of air-

damped tuning forks of different natural frequencies.

All took their cue from the suggestion, given in the question, that if a ceramic magnet was

attached to the tuning fork, then the oscillations of the (now magnetised) prongs could induce

a voltage in the coils of a search coil placed in close proximity to the tuning fork. Many

candidates showed that they understood that the induced voltage resulted from changing flux

linkage with the search coil, but while assuming that the size of this voltage would be

affected by the amplitude of the tuning fork oscillation, all chose to ignore that the frequency

of the oscillation would also affect the rate of flux linkage and hence the induced voltage.

This oversight was not penalised nor did examiners deduct marks if candidates assumed that

the size of the induced voltage decayed linearly as the oscillations of the tuning fork died

away.

The diagrams produced contained details that in many instances would have prevented the

plan working. Cells, variable resistors and the like were liberally used but as long as some

recognisable method by which either an induced voltage or current could be measured was

shown credit was usually given. Few seemed to appreciate the need to insist on a meter that

would detect the alternating signal produced but some ingeniously used diodes to allow for a


24

measure of rectification. The better answers sensibly incorporated an oscilloscope and in

some cases this led to a profitable discussion of how the uncertainty in the amplitude could be

reduced by a prudent choice of Y-gain.

Candidates were expected to explain that some characteristic of the electrical signal would be

monitored continuously over the interval while the amplitude decayed, requiring the use of a

stopwatch (not, as some insisted ‘a timer’). Good alternative approaches using data loggers

were accepted but candidates who chose this path had to demonstrate a secure grasp of the

terminology: for full credit it was expected that candidates should refer to the use of a voltage

or current sensor and go on to explain how the data would be retrieved and analysed

graphically.

Many candidates gave a sensible procedure of how they would analyse the data obtained,

usually writing about a graph of voltage against time to measure the rate of decay or, in cases

where an exponential decrease in amplitude was predicted, a measurement of half life was

suggested. Some candidates gave rather vague accounts about measuring the time for the

signal to dissipate, often neglecting to explain how a fair comparison would be made between

the different tuning forks.

Most candidates explained that they would repeat the procedure with a range of tuning forks

and full credit was given if they went on to explain that the parameter measured before (rate

of decay or half life) was then compared graphically with the natural frequency of the tuning

fork.

A few candidates became side-tracked and ended up describing procedures to measure the

natural frequencies of the forks. It was interesting to note how many thought that the

oscilloscope trace could provide a measure of wavelength and then by manipulation of c = fλ,

the frequency would be found.

The methods chosen to set the tuning forks in motion were not always as might be

anticipated. A number of accounts were seen in which the circuit connected to the search coil

included a variable frequency supply that was used to drive the tuning fork until its resonant

frequency was found. The supply was then switched off and the amplitude of the oscillations

allowed to die away. It was more generally the case that the tuning fork was struck and then

placed closed to the coil. Some candidates saw how hard it was struck as a control measure

but the methods of achieving this were unconvincing and gained no credit. For the control

mark, candidates were expected to state that the distance between the coil and the fork was

maintained as the oscillations decayed.

Previous reports have emphasised that in describing precautions to overcome difficulties,

candidates should direct their arguments to the measuring being done. Credit was given for

measures that made the amplitude of the electrical signal easier to measure, either by

increasing the resolution of the vertical scale on the oscilloscope or by using stronger

magnets and/or increasing the turns on the search coil. More ingenious were the suggestions

that causing an air column to resonate could establish if the tuning fork was correctly

calibrated; some candidates suggested the use of a microphone and oscilloscope to calibrate

the tuning forks and this too was given credit. It is still comparatively rare to find the

procedure justified by identifying the difficulty it seeks to overcome. As ever, there was a

spate of generalised and vague comments about repeating the experiment and averaging,

which gained no credit.


25

Question 2

Candidates were required to measure the time for the pd across a capacitor to fall by 50%.

The capacitor discharged through a resistor network, the resistance of which could be varied

by shorting out various resistors using a lead.

While most candidates saw quickly what this entailed, a surprising number decided that the

resistance through which the capacitor was discharging was actually the resistance they were

shorting out and produced graphs that went the wrong way. It was only these candidates who

failed to get the mark for the initial halving time, T0.

A small number thought that measuring the pd across the capacitor at regular intervals was a

better way to determine the time for the pd to halve: their work quickly became congested

with data although some laboriously found a decay constant and from that a half life. Few

chose the path of finding the time for successive halving of pd, e.g. finding the times for

8 ,

4 ,

2

000VVV

etc., but the majority simply repeated the timing between V0 and 2

0V

which earned

full credit. Some failed to include all the different resistances that could be produced by

different shorting arrangements: the most common omission was that of 12.2 kΩ produced by

shorting out the 4.7 kΩ resistor.

Poor or careless tabulation sometimes accounted for lost marks and occasionally tried the

patience of the examiner but in general it was common to find all six marks awarded for

tabulation, data and use of significant figures in the results.

Because the quoted resistances rarely deviate from the advertised values, careful timing made

the graph an easy proposition for most candidates. With the maximum resistance being 16.9

kΩ, the horizontal scale effectively filled the width of the page, and providing a false origin

was used on the vertical scale, practically all of the page could be used: this almost invariably

enabled an accurate determination of the gradient to be made. It was odd to find some

candidates were unduly influenced in their choice of best-fit line by the odd anomalous result:

there was no suggestion in the scripts seen that candidates were pressed for time so checking

of dubious data should have been possible.

Candidates were expected to produce a value for G

T0 in the range 11.5 kΩ to 12.5 kΩ, which

many were able to do, but marks were lost for missing units (or missing the ‘k’ in kΩ) or the

occasional 5 significant figure result.

In part (e), assessing AO3d, many candidates had mixed fortunes. A majority gained a mark

in (e)(i) for stating that the uncertainty was largest when the T values were shortest but only

gained full credit if they also explained that this was when the voltmeter reading was falling

at a rate that made it difficult to judge when the pd had reached the desired value.

In (e)(ii) the majority realised that using a lower resistance analogue meter in parallel with

the capacitor reduced the circuit resistance, thus speeding up the rate of discharge and making

T smaller for each value of R. Thereafter many came unstuck by forgetting that the

parameters being plotted along the horizontal axis was the advertised resistance and not the

reduced value produced by virtue of the presence of the voltmeter. They therefore said the

graph line would shift leftwards making the intercept higher. Fewer candidates realised that

the changed resistance affected each reading differently and very few could correctly predict


26

that the new graph would not just have a lower intercept but would thereafter curve upwards

at a decreasing rate. Full credit was given if it was suggested that the new graph would have a

lower intercept and lower gradient. Many candidates did not see the need to sketch a graph

that showed a straightforward comparison between the outcome of the experiment they had

performed and that suggested by use of the analogue voltmeter suggested. A single line

graph made it very difficult for credit to be given unless some numerical values were given

on the axes. A number of candidates were clearly under the impression that when the

resistance of R exceeded 10 kΩ (the resistance of the voltmeter) then all the current would

pass through the voltmeter: this, they claimed would produce a cranked graph in which T

would become constant as soon as R exceeded 10 kΩ. Others, thinking along the lines

suggested in (e)(i) and similarly unsuccessfully, suggested that the use of the analogue

voltmeter reduced the scatter in the graph produced when they used the digital voltmeter with

the 2 Hz refresh rate.

Units 5 - 9 : PHAC : Coursework

In most cases Centres used investigations which were appropriate, allowing their candidates

access to the full range of assessment criteria. Experiments on simple harmonic motion,

optical experiments on lenses and charging/discharging capacitors were the most popular, and

these proved to be successful in allowing a full range of marks to be achieved.

The general comments on presentation of coursework and issues raised by moderators are the

same as those made on the AS work. Please refer to the detailed comments which appear on

pages 13 - 15 of this report.

Units 5 - 9 : PHA5/W - PHA9/W : Section A : Nuclear Instability

The question set on the nuclear instability specification yielded reasonable answers but very

few candidates scored full marks. The three transitions required in part (a) were frequently all

correct, although the arrows representing A and C seemed to be randomly chosen in many

scripts. The arrow representing B was correct more often than not. The most common mark

for part (a)(ii) was zero; the majority of candidates did not recognise the need for an electron

on the left hand side of the equation and almost all of those who realised that a neutrino of

some sort was required on the right hand side made it an antineutrino. In most cases the

daughter nucleus was represented by an X and had the wrong subscripts and/or superscripts.

Several candidates attempted the equation in terms of protons, neutrons and positrons. No

credit was given for such an equation.

There were many correct calculations in part (b), although a mark was lost in part (iii) by

giving 4.18 × 10−13

(J) as the answer, rather than considering the transition from the 1.63 to

the 1.33 energy level. As a consequence of error carried forward, part (iii) usually provided a

mark.

It was unfortunate that there occurred a small printing error in the data of figure 2 in part (b)

which involved the factor of 10−13

in the energy levels being obscured.. This only occurred in


27

the option papers for unit 5 and unit 7. The examiners were fully aware of the error and no

candidate lost marks because of it.

Most candidates in part (c) gave two precautions although many stated the same precaution

twice. A sizeable minority only gave the precautions and ignored the 'explain' part of the

question. Considering the title and subject coverage of the unit it was surprising to find that

many candidates ignored the radioactive nature of the isotope and laboured under the illusion

that magnesium is wont to burst into a brilliantly white flame if exposed to the

atmosphere/water/dampness, therefore requiring dark glasses, a perspex screen, asbestos

gloves and full breathing equipment. There were some very sensible answers related to the

context of a school laboratory, most of them involving keeping the source at some distance

from the body or handling it with tongs, storing the magnesium in a lead pot when not in use,

using the magnesium only for short periods or using some kind of screening, including a

metre or so of air. Credit was usually given to part (c)(ii) if the penetrating power of the γradiation or the ability of the β radiation to cause ionisation was discussed.

Unit 5 : PHA5/W : Section B : Astrophysics Option

General comments

The general difficulty of questions was in line with previous years. The performance of

candidates, as in previous years, ranged from those who clearly understood the astrophysics

topics and who had used past papers for practice, to those who could demonstrate very little

knowledge or understanding at all.

Question 2

Part (a), which required a ray diagram of the Cassegrain telescope was, in general, answered

quite well. Candidates should, however, be encouraged to use a ruler and pencil when

drawing rays and to include arrows to show the direction of the light. Errors which occurred

frequently were: drawing the second mirror as a concave mirror and drawing the objective

lens with too much curvature, so that, with the gap, it looked like two separate concave

mirrors. Candidates who drew a Newtonian reflector were awarded only one mark and that

for the first reflection. Candidates who drew a refracting telescope gained no credit.

In part (b) candidates needed to draw a correct diagram, with the rays crossing correctly, to

obtain full marks. It was common to see the focal point for the more axial rays closer to the

mirror than the focal point for rays further from the axis. Another error was the foci not being

on the principal axis. Some candidates incorrectly suggested that the aberration was due to

imperfections in the surface of the mirror and several believed that spherical aberration was

the bringing together of light to a single focus (confusing the diagram with that for a

paraboloidal mirror).

A correct ray diagram illustrating chromatic aberration was required for full credit in part (c).

The labelled focus for blue light should have been closer to the lens than the focus for red

light. Candidates who attributed the effect to diffraction were not given credit, although it

was clear that the candidates were confused between the meaning of the words diffraction


28

and refraction. Although the use of two prisms in the diagram was tolerated, because

presumably that was how the effect had been explained, the written answer had to refer to

lenses. Any answer involving mirrors in both the diagram and written part earned no credit.

Question 3

The calculations in part (a) were usually correct. Many candidates gave the distance in part

(i) in megaparsecs, which made handling the units in part (ii) a little easier. There was a

tendency for weaker candidates to work backwards in part (ii) and thus doctor their answer to

part (i). In effect, these candidates made two errors, one with the units of Hubble’s constant

and the second with the velocity of the galaxy. This was despite the fact that the unit of

Hubble’s constant is given on the data sheet. These efforts were not awarded. The unit of

km s−1

also caused problems in part (iii) and many candidates obtained a value of 2 x 10−12

m

for the change in wavelength. Some credit was still given if the candidates showed that this

wavelength was added to the laboratory based wavelength (red shift) and not subtracted.

In part (b) it was clear that many candidates knew that tH

= 1and hence obtained

v = Hd and vd

t= , but very few explained how t gave the age of the Universe. The expected

assumption was associated with the value of the Hubble constant, as this is the value quoted

in the specification. Credit was given to some alternatives. Candidates who described a

graphical method to explain how the age of the Universe could be obtained, showed the best

understanding of the topic.

Question 4

The Hertzsprung-Russell diagram comes in many forms but candidates should be encouraged

to learn the one which has appeared in many published mark schemes. The absolute

magnitude scale should go from +15 up to −10 and the temperature scale from 50 000 K to 2

500 K. Credit was still given if the answers fell within a range around these values. It was not

necessary for candidates to label the spectral class on the horizontal axis this time. Dwarf

stars and giant stars were indicated correctly very often, but the main sequence was

sometimes drawn as a line rather than a band and the shape was also drawn incorrectly on

numerous occasions.

It was pleasing to note in part (b), how many candidates knew what caused the main spectral

lines, although some answers were ambiguous and listed too many possible suggestions for

any credit.

The argument and reasoning expected in part (c) has been examined on numerous occasions

in this unit and candidates should be aware of the correct sequence. Antares was usually

correctly identified as the larger star. Most candidates also knew that M class stars are cooler

than O class stars, but there was considerable confusion about which star was brighter, with

some candidates discussing the difference between real and apparent magnitude. The best

answers stated that they had the same brightness and therefore the cooler star had to be bigger

to give out the same amount of light, quoting Stefan’s law to support their argument. It was


29

not sufficient for candidates to refer to the absolute magnitudes being the same; this had to be

related to luminosity, power output or brightness. There was ample scope here for candidates

to demonstrate their ability to write clearly, using correct spelling, punctuation and grammar

and to structure their answers in a coherent way.

Question 5

Part (a) gave candidates an opportunity to show what they knew about some of the more

spectacular phenomena in the Universe. Most knew that a supernova was short lived and

referred to explosions. It was not sufficient to state that they were bright or gave out a lot of

energy without a reference to a time scale. There are many possible properties of neutron

stars, although the high density was deemed to be the one that all neutron stars had in

common. Stating that they were made up of neutrons was interpreted as an example of

tautology. The significant property of a black hole is the fact that its escape velocity is

greater than the speed of light. References to high density (or singularities) were not

credited. The concept of a black hole predates the ideas of singularities and there are other

objects which are also extremely dense.

Part (b) was well answered, although careless mistakes were common. As stated in previous

reports, candidates often fail to look up the correct mass from the data sheet or forget to

square the speed of light when carrying out the calculation.

Unit 6 : PHA6/W : Section B : Medical Physics Option

General Comments

All the questions proved to be accessible to the candidates and very few questions were not

attempted. Although the mathematical demands of the paper were not excessive, many

candidates failed to cope with the logarithmic calculation in question 4(b). It was again

noticeable that in all the descriptive answers there was a lack of clarity which often resulted

in marks not being awarded. Although candidates were told which sections would be

scrutinised for the quality of written communication marks, many failed to write in coherent

sentences, failed to use capital letters or correct punctuation.

Question 2

Most candidates found, in part (a), an easy introduction to the paper and were able to draw

the path of the two rays correctly, thus scoring both marks. Some candidates however,

showed the lens acting as a diverging lens and were subsequently penalised. Although it was

considered to be an easy introduction, a significant number of candidates did not attempt it.

In order to give candidates a starting point to part (b), the fovea was marked on the diagram.

This was picked up by many of the candidates who then proceeded to give the required

answer. The recurring error in the answer was the statement that rods were found at the

fovea.


30

Both parts (c) and (d) were answered well by nearly all the candidates, except that in part (d)

many candidates thought that accommodation referred to dark adaptation.

Question 3

Answers to this question were, in general, the poorest on the paper. In part (a), for example,

many candidates failed to score any marks. The most common errors for the potential

difference axis was having the wrong units, which included V, µV and eV, and also the

wrong scale, which should have been from –30 to + 70 in mV. A common fault for the time

axis was the use of seconds rather than ms as the unit.

The answers to part (b) were better than those to part (a), but many candidates failed to obtain

full marks because of poorly expressed answers. Several candidates referred to sodium ions

moving out of the membrane and potassium ions moving in, rather than the other way

around.

Question 4

The majority of candidates scored high marks on part (a); marks not awarded were usually

due to a failing to describe the function of the ossicles clearly enough.

The calculation in part (b) proved difficult for the majority of the candidates. Some

candidates treated 42 dB as the intensity and worked out an intensity level. Other candidates

were able to insert the correct numbers into the relevant equation, but were then unable to

calculate the final answer correctly. Several candidates worked out the final answer

correctly, but lost a mark by failing to give the correct unit.

Question 5

This question was, in general, answered well, but many candidates wrote a great deal,

especially in part (b) and gained no marks. In part (a) many wrong ideas were encountered,

especially in part (i). These including “focussing the beam more”, “increasing the distance

between the beam and the patient” and “increasing the angle of the bevelled edge”. In nearly

all cases it was found that if a candidate was able to give a correct method in part (i) then the

correct effect was given in part (ii).

Although many candidates failed on part (b), full marks were gained sometimes. The main

error was a failure to use correct terminology. Several candidates referred to X-ray intensity

when they meant X-ray photon energy. Other candidates wrongly based their answer on the

use of the grid in front of the detector to stop scattered X-rays.


31

Unit 7 : PHA7/W : Section B : Applied Physics Option

General Comments

Almost all candidates attempted all the questions and there was no evidence of a lack of time

in answering the paper. All the questions were accessible and all questions saw scores of full

marks. Many candidates incurred the significant figure penalty, almost always in question

2(b)(iii), by giving their answer to 5 significant figures or more. Few candidates gave the

correct units to all three of the numerical answers in question 2(b)(i)(ii) and (iii) and many

did not give the correct unit of moment of inertia in question 3(b)(ii). Mathematical

manipulations were generally good, including the pVγ = constant calculation in question 4.

The quality of written English in most scripts was good enough to express clearly what the

candidate was attempting to say but grammar, spelling and punctuation were, in a large

number of cases, clearly not of much interest to the candidate.

Question 2

Most candidates answered part (a) correctly, including the correct unit. Having correctly

calculated the angular speed, many candidates then regressed to translational units and

proceeded to the end of the question with an indiscriminate mix of rotational and translational

quantities, which was difficult to sort out. Very few candidates in part (b) gave the correct

units for the answers in all three sections. The unit of torque is N m; this is not the same as J

since, in the case of torque, the force and the distance are not in the same direction. N m and

J are distinct and distinctly different. For the same reason, the unit of angular impulse is not J

s; the unit of angular impulse is N m s or kg m2 (rad)s

-1.

Those candidates who stuck to rotational units generally managed to arrive at a correct

answer to part (iv) in terms of radians, but some candidates did not convert radians to turns as

required by the question. The concept of 'complete turns' was understood by so few

candidates, including the most able candidates, that the mark scheme needed adjustment: 3.2

complete turns was accepted as correct.

Question 3

This question was intended to be very straightforward but turned out to be otherwise. In part

(a)(i) the most common answer for the torque was 2.4, which is the force of 0.60N multiplied

by four. The most common unit for this torque was a permutation of kg, kg2, m, m

2, rad, r,

c,

s-1

and s-2

, often not related to the unit of torque given in the previous question. Where the

same wrong unit of torque appeared as in question 2(b)(ii) (most usually kg m2 rads

-2) the

unit penalty was not applied twice. The power dissipated by the frictional couple in part

(a)(ii) was often calculated as it should be using P = Tω, albeit using a wrong value of torque,

but the ‘showing your reasoning’ was totally ignored by all but a handful of candidates. As

the platform is rotating at a steady angular speed, the applied torque from the water jets must

be equal to the frictional torque on the platform.

Having arrived at a correct answer, occasionally completely correct including the unit of

power, a significant number of candidates then 'corrected' the correct answer to give a wrong

answer after trying part (b)(i) and getting it wrong. This overwhelming temptation to adjust


32

the answer to part (a)(ii) was only absent in candidates who arrived at an answer to part (b)(i)

consistent with their previous answer, because of their mistake in part (a)(i). There were

candidates who resisted this temptation but offered no explanation. One or two of the best

candidates realised that the average power during the slowing down process was half the

maximum power. Very few candidates arrived at the correct answer, perfectly legitimately,

by calculating the work done in terms of W = Tθ, which bypassed the issue of average power.

Most candidates arrived at a correct numerical answer to part (b)(ii). The unit of moment of

inertia was in the data of question 2(b)(ii), but many candidates nevertheless omitted it

altogether or gave a wrong unit.

Question 4

In part (a), most candidates, but by no means all, took the data in the question as a broad hint

and used pVγ = constant to calculate the new volume of air in the pump. In a considerable

number of scripts, (pV)γ = constant apparently also led to the correct answer, as did Vp

γ =

constant. The ‘show that’ in the question required a convincing attempt at the mathematics.

Part (b) was answered correctly by the majority of candidates. Weak candidates failed to

convert temperature to Kelvin and a surprising number of those who made the attempt,

arrived at a value of 300 K.

Part (c) was very well done by the majority of candidates, including a fair proportion of

weaker candidates, all of whom seemed to have an intuitive feel for the physics of the

situation. Not all of them managed to convert convincing reasons into a correct statement,

but the general level of understanding was gratifying. In all but a few cases, and despite the

experience of previous questions of this sort, the suggestion that a pV diagram might be

helpful was wildly optimistic on the part of the examiner.

Question 5

Almost all candidates knew that the area enclosed by the rectangle was what they were

looking for initially. Many candidates found it, some correctly but many incorrectly. Some

multiplied their answer by 1, some by 0.2 and some, correctly, by 5 to find the power. Most

candidates could manage one of the two marks.

Part (b) was answered very well indeed by most candidates. In many answers the detail and

analysis given by the candidate exceeded the requirements of the mark scheme and most

answers showed a sound understanding of the indicator diagram.


33

Unit 8 : PHA8/W : Section B : Turning Points in Physics Option

General comments

Most candidates were able to attempt most, if not all the questions, although some candidates

scored badly in certain sections as a result of not reading the relevant part of the question

with sufficient care. Most candidates made good progress on the calculations, the solutions

of which were generally set out clearly with appropriate use of significant figures. Correct

units were usually given. Poor answers to descriptive questions were not uncommon, often

because candidates failed to identify key words or phrases in the question. Many candidates

were able to score both marks for their quality of written communication.

Question 2

In part (a)(i) most candidates were able to give the correct direction of the electric field. In

part (ii), a significant minority attempted to calculate the charge of the oil droplet by either

considering the mass of the droplet as 1 kg or neglecting the mass altogether. Many other

candidates knew that the question required a calculation of the charge/mass ratio for the

droplet, but gave their explanation in terms of the charge, e, of the electron instead of the

charge on the droplet.

When explaining the effect of switching off the electric field in part (b), most candidates

knew that the drag force equalled the weight of the droplet at the terminal speed. A

significant number of candidates however, did not make it clear that the drag force increased

as the speed increased. Few candidates mentioned that the droplet accelerated initially due to

its weight or that the acceleration became zero at terminal speed.

Question 3

Although most candidates knew, in part (a)(i), that the fringes were due to interference

between two beams, few candidates mentioned that the two beams reached the observer.

Many candidates were confused about the general conditions for a bright fringe or a dark

fringe and often referred to phase difference in terms of wavelength, or gave the path

difference for a dark fringe as half a wavelength instead of an odd number of half

wavelengths.

In part (a)(ii), most candidates were aware that the ether theory was abandoned as a result of

the Michelson-Morley experiment, but very few were able to explain in adequate terms,

either why a fringe shift was predicted using the theory or why such a shift was not observed.

Few candidates mentioned that the beams were realigned relative to the Earth's direction of

motion or that the time taken by light to travel along each path and the distance travelled was

unchanged, when the apparatus was rotated.

There were some very good explanations of Einstein’s postulate in part (b) and many

candidates scored both marks. Some candidates made irrelevant references to frames of

reference.


34

Question 4

Candidates who scored well in part (a)(i) usually referred to electron diffraction and were

able to provide a description of a piece of relevant evidence. Some candidates however, did

lose a mark through vague references to diffraction (of electrons) at a slit. Many candidates

provided irrelevant answers to both part (i) and part (ii) as a result of not realising the

question asked about matter.

The few good answers seen in part (a)(ii) usually referred to the deflection of a beam of

electrons or protons by an electric or a magnetic field. Some candidates lost a mark by

referring to the deflection of such a beam by a gravitational field. Some candidates scored

well by describing ionisation by collision or scattering of alpha particles by nuclei. A

significant number of candidates lost marks by describing evidence of the particle-like nature

of light.

In the calculations in part (b), many candidates scored all possible marks with clearly

explained calculations. Those who attempted to calculate the de Broglie wavelength using

the voltage formula were often confused between the speed and the voltage, or else failed to

include e in their calculation. Almost all candidates who chose to calculate the de Broglie

wavelength directly from the speed did so correctly.

Question 5

In part (a) the majority of candidates knew that in the situation described, the force was

perpendicular to the direction of motion and was therefore centripetal. Not many candidates

however, mentioned that the force causes the direction of motion to change or that it does not

change the speed. Only a small minority knew that the velocity is tangential to the path.

Many candidates failed to provide an adequate derivation, in part (b)(i), for the speed, even

though they produced the required equation. Many candidates scored both marks in part

(b)(ii) although a significant minority calculated the charge of the electron rather than its

specific charge.

Unit 9 : PHA9/W : Section B : Electronics Option

General Comments

The response to this paper was very similar to that of last year. Although many candidates

performed very well, there was a very long tail in the distribution curve. These weaker

candidates gave very poor answers and the examiners were left wondering whether many of

them had in fact been prepared for an electronics examination. Their basic knowledge of

electronics was sadly non-existent.


35

Question 2

There were three very accessible marks in part (a), obtained by drawing the graph correctly.

Most candidates gained these marks but thereafter, calculating the capacitance from the

graph, was poorly done with few candidates obtaining the correct answer. The majority of

candidates were content to calculate the gradient of the graph and equate that to the

capacitance, ignoring the 1

2πV factor.

Part (b)(i), in general, realised good answers. Most candidates knew that the reactance

decreased as the frequency increased and so came to the correct conclusion. Part (ii) likewise

produced correct calculations, allowing for an incorrect value of the capacitance carried

forward from part (a). Part (iii) however, was a matter of guesswork. Very few candidates

realised that at low frequencies, Vout ≈ Vin and hence that the ratio of the two voltages → 1.

Question 3

The most difficult part of this question, as far as the candidates were concerned, occurred in

part (a)(i) where they had to give the approximate voltage at the base of the transistor. A

worrying number gave this as 12 V, not realising that the base was connected to 0 V line

through the switch. This incorrect answer, of course, caused problems in the next section and

also in part (b). Candidates with the correct voltage at P gave very clear explanations of why

the alarm was off.

(b) Usually a correct part (a) led to a correct part (b) but it was worrying to find a large

number of candidates stating that the voltage was now forced to flow into the transistor.

The explanations in part (c) suffered from the inability of candidates to express themselves

clearly. The examiners had the impression that the candidates realised that there was a

separate path for current between the 12 V supply and the 0 V line which did not involving

the transistor, but the number of candidates who could explained this clearly were in the

minority. The answer to part (d) was usually correct.

Question 4

A large number of candidates calculated the correct switch over voltage in part (a). In part

(b) it was pleasing to see that a majority of candidates had drawn the LED between the output

and 0 V or between the output and the 12 V supply. In addition, the direction of the diode

was usually correct and also the calculation for the value of the series resistor.

Part (c) proved to be more difficult, but many candidates successfully carried out the

calculation giving the resistance of the LDR and subsequently read correctly the light

intensity from the graph. Other candidates did not know where to start and made a guess at

the resistance. If no effort had been made to calculate the resistance, there was no carry

forward error for the value of the intensity.


36

Unit 10 : PA10 : Synoptic Unit

General Comments

The paper provided plenty of opportunities where candidates could score marks using the

skills and knowledge developed over the course. In general, candidates found the descriptive

questions harder to answer than the calculations, which were mostly straightforward. Most

candidates knew how to explain and carry out a calculation. Weaker candidates, in general

were able to score some marks in most, if not all questions, even if they were often unable to

work through the longer calculations. The very best candidates coped well with the more

difficult calculations including those in questions 5 and 6. However, these two questions did

provide a challenge for other candidates, who nevertheless scored well elsewhere. The graph

question (Q5) enabled weak candidates to score marks through data handling and graph

plotting. Units were generally correctly given. The quality of written communication was

generally good. Few candidates seem to have been short of time.

Question 1

Many candidates scored all three marks in part (a)(i), but some were careless and used the

given value of diameter for the radius or did not include π in their calculations. A few

candidates lost the final mark as a result of giving the answer to too many significant figures.

In part (ii), although some candidates confused speed with angular velocity , many correct

answers were seen using v

r

r

2

or 2ω . Candidates who repeated the error of using the value of

the diameter rather than the radius were not penalised again.

In part (b) most candidates knew that the effect was due to resonance but not all of them were

able to provide a clear explanation of why resonance occurred at a particular rotational speed

of the motor.

Question 2

Part (a) proved to be very accessible and many candidates scored full marks. Most

candidates calculated the resistor pd as 0.8 V and then calculated the resistance, as expected.

Other candidates however, calculated the total circuit resistance, then the diode resistance and

obtained the required resistance by subtraction. In this particular problem some candidates

used an incorrect pd and were not awarded any credit. Many clear and correct answers were

seen in part (ii).

The energy of the photon was calculated correctly in part (b) by many candidates, but some

failed to score because the wavelength was taken as 1/f or because the energy was taken to be

½QV. The general principle behind the question in part (ii) was understood by most

candidates and many correct answers were seen. A small minority of candidates however,

calculated and used the power supplied to the resistor and not the diode.


37

Question 3

Part (a) produced good results and many candidates scored full marks, although some were

not aware of the expression for efficiency. Other candidates forgot to take account of the

area in part (ii) and thereby lost a mark.

Many candidates provided a clearly explained calculation in part (b)(i). Candidates who

failed to score both marks usually made an arithmetical error in the conversion from MeV to

J. The most common error in part (ii) was the failure to include the appropriate unit of s−1

or

year−1

for the decay constant. Weaker candidates made poor progress in part (iii), often being

unaware of how to proceed or making a pointless attempt to use the radioactive decay

equation. Incorrect answers by the better candidates arose because the decay constant was

not converted to s−1

for use in part (iii) or through failure to use the mass number correctly or

converting mass, given in atomic mass units, into kg.

Question 4

This question produced many high marks. The usual error was failing to calculate the area

correctly in m2, usually through multiplying by 10

3 instead of 10

6. Only the very best

candidates realised in part (ii) that the centre of gravity of the water dropped by

5 m and not 10 m. In part (iii) most candidates knew how to calculate the average loss of

gravitational potential energy per second and how to use the efficiency correctly.

Question 5

This data handling and graph question carried the highest marks on the paper. When

describing the motion of the ball bearing in part (a)(i), the majority of candidates were aware

that the object accelerated initially and then reached terminal speed. Few however, realised

that the acceleration became zero and some incorrectly thought that the acceleration was

constant even though they stated it had reached terminal speed.

When explaining the motion in part (ii), many candidates failed to state clearly that the drag

force increased with increase of speed. Most candidates knew that the drag force became

equal to the weight of the ball bearing but often failed to state that the two forces opposed

each other and therefore produced a zero resultant force, leading to zero acceleration at the

terminal speed.

Calculation of the data in part (b) was done very well, except that some candidates were

careless in the use of significant figures and were penalised. Other candidates gained no

credit at all through using an incorrect distance to calculate the speed.

In part (c), almost all candidates scored the mark for correct data in column E in the table.

Many also scored full marks in part (ii). Penalties were incurred through omission of labels

on the axes of the graph or failure to plot the points correctly. Surprisingly, many candidates

misplotted the datum 2.07 in column E as 2.007. Best fit lines were usually appropriately

drawn.

In part (d) it was pleasing to see that many candidates used logs with confidence and

expressed the equation v = krn

in the required form of y = mx + c. In part (i), full marks were


38

often scored with a clear gradient triangle, an appropriate calculation and a clear statement

that n is equal to the gradient. Some candidates thought that n was the intercept and k the

gradient. However, many candidates did use the intercept correctly and obtained the correct

value of k. A significant number of candidates approached the same point, and gained the

same credit, by using the value of n obtained previously, together with the co-ordinates of a

point on the line in the equation v = krn to calculate k. Very few candidates were able to give

the correct unit of k.

Question 6

In this question most candidates were aware that, in part (a), with the powder present the air

was forced into a smaller volume. However, a majority of these candidates failed to provide

an adequate explanation of why the pressure increased. Instead of stating that p ∝ 1/V all that

was given was that the pressure increased because the volume was less. In part (a)(ii) many

of the solutions did not indicate that

pV = constant. A significant number of candidates attempted inappropriate physics by using

force per unit area instead of p × V and subsequently scored no marks, even though volume

values were used for the areas and the correct numerical answer was obtained.

The majority of candidates calculated the correct volume of the powder in part (b)(i) but only

the best candidates were able to score full marks in part (ii) as many candidates used the

initial volume from part (b) and failed to subtract the powder volume. The best candidates

demonstrated a clear understanding of the principles involved and used the powder volume

correctly at each appropriate stage. As in part (a) , some candidates attempted to use

incorrect physics and were awarded no marks. Candidates who used the correct principle

usually came to a valid conclusion, even if they failed to subtract the powder volume at the

start.

Question 7

Most candidates were awarded full marks in part (a) although some candidates added 273 to

the temperature difference. A few candidates lost the mark in part (ii) because they failed to

describe the correct relationship between power and energy.

In part (b)(i), a significant number of candidates obtained the correct value of current but then

divided, or multiplied, by 2 , clearly unaware that the required answer had already been

obtained. In part (ii), many candidates scored full marks with a clear and carefully expressed

calculation, but a few candidates did lose one or more marks as a result of failure to use the

correct value for the radius or the correct expression for the cross-sectional area. A

significant number of candidates were awarded only one mark in part (iii) because they had

not obtained the correct value of resistance per metre in part (ii) or else they failed to

appreciate that the cable contained two wires. In general, candidates who scored well in part

(ii) usually scored both marks in part (iii). In part (iv), most candidates gained the available

mark, including weaker candidates who were unable to make progress in the earlier parts of

part (b).


39

Question 8

It surprised the examiners that only a minority of candidates gained full marks in part (a).

Successful solutions were usually based on the triangle of forces. Only the best candidates

resolved the tension into components and equated the components to the weight and the

electrostatic force respectively. Many candidates incorrectly resolved the weight into

components parallel and perpendicular to the thread.

The majority of candidates obtained the correct value of the electric field strength in part (b)

and were able to make good progress in part (ii). Candidates who equated g to 10 N kg−1

or

rounded off incorrectly at the end were penalised. Other candidates attempted inappropriate

solutions involving Coulomb's law and did not realise that the force = qE. A small minority

of candidates attempted incorrectly to relate the gain of gravitational potential energy to an

electrostatic energy formula such as ½QV.


40

Mark Ranges and Award of Grades

Unit

Maximum

Mark

(Raw)

Maximum

Mark

(Scaled)

Mean

Mark

(Scaled)

Standard

Deviation

(Scaled)

PAO1 50 50 26.1 11.2

PAO2 50 50 28.0 12.2

PHA3/W – Written 50 50 28.4 11.4

PHA3/C – Coursework 30 30 21.5 5.8

PA3C 80 80 49.9 15.2

PHA3/W – Written 50 50 31.2 11.2

PHA3/P – Practical 30 30 16.5 5.3

PA3P 80 80 47.7 15.1

PAO4 45 60 30.9 12.0

PHA5/W - Written 40 60 19.9 8.1


PA5C 70 90 53.0 15.1

PHA5/W - Written 40 60 20.6 8.1

PHA5/P – Practical 30 30 18.9 4.3

PA5P 70 90 50.0 14.7

PHA6/W – Written 40 60 22.3 7.5


PA6C 70 90 57.4 14.2

PHA6/W – Written 40 60 20.9 7.9

PHA6/P – Practical 30 30 17.6 4.3

PA6P 70 90 49.2 14.7

PHA7/W – Written 40 60 21.5 9.0


PA7C 70 90 56.3 16.8


41

PHA7/W – Written 40 60 22.5 9.0

PHA7/P – Practical 30 30 20.4 4.4

PA7P 70 90 54.5 16.5

PHA8/W – Written 40 60 17.1 8.2


PA8C 70 90 48.5 15.8

PHA8/W – Written 40 60 19.7 7.7

PHA8/P – Practical 30 30 19.3 4.2

PA8P 70 90 49.1 14.0

PHA9/W – Written 40 60 19.6 9.1


PA9C 70 90 52.9 15.8

PHA9/W – Written 40 60 21.7 8.8

PHA9/P – Practical 30 30 19.7 4.0

PA9P 70 90 52.5 15.6

PA10 80 80 48.0 16.5

For units which contain only one component, scaled marks are the same as raw marks.


42

PAO1 Particles, Radiation and Quantum Phenomena

( 7221 candidates)

GradeMax.

markA B C D E

Scaled Boundary Mark 50 36 31 26 22 18

Uniform Boundary Mark 90 72 63 54 45 36

PAO2 Mechanics and Molecular Kinetic Theory

(8040 candidates)

GradeMax.

markA B C D E



PA3C Current Electricity and Elastic Properties of Solids

Coursework

(5275 candidates)

GradeMax.mark

A B C D E

raw 50 39 34 29 24 20PHA3/W Boundary

Mark scaled 50 39 34 29 24 20

raw 30 25 22 19 16 13PHA3/C Boundary

Mark scaled 30 25 22 19 16 13

PA3C Scaled Boundary Mark 80 64 56 48 40 33

PA3C Uniform Boundary Mark 120 96 84 72 60 48


43

PA3P Current Electricity and Elastic Properties of Solids

Practical

(3349 candidates)

GradeMax.

markA B C D E


Mark scaled 50 39 34 29 24 20

raw 30 21 18 15 13 11PHA3/P Boundary

Mark scaled 30 21 18 15 13 11

PA3P Scaled Boundary Mark 80 60 52 44 37 31


PAO4 Waves, Fields and Nuclear Energy

(4481 candidates)

GradeMax.

markA B C D E




44

PA5C Astrophysics Coursework

(1383 candidates)

GradeMax.

markA B C D E


Mark scaled 60 44 39 35 30 26


Mark scaled 30 26 23 20 17 14



PA5P Astrophysics Practical

(389 candidates)

GradeMax.

markA B C D E


Mark scaled 60 44 39 35 30 26


Mark scaled 30 23 21 19 17 15


PA5PC Uniform Boundary Mark 90 72 63 54 45 36


45

PA6C Medical Physics Coursework

(466 candidates)

GradeMax.

markA B C D E


Mark scaled 60 44 39 35 30 26


Mark scaled 30 26 23 20 17 14



PA6P Medical Physics Practical

(181 candidates)

GradeMax.

markA B C D E


Mark scaled 60 44 39 35 30 26


Mark scaled 30 23 21 19 17 15


PA6P Uniform Boundary Mark 90 72 63 54 45 36


46

PA7C Applied Physics Coursework

(380 candidates)

GradeMax.

markA B C D E


Mark scaled 60 45 41 36 32 27


Mark scaled 30 26 23 20 17 14



PA7P Applied Physics Practical

(313 candidates)

GradeMax.

markA B C D E


Mark scaled 60 45 41 36 32 27


Mark scaled 30 23 21 19 17 15




47

PA8C Turning Points in Physics Coursework

(814 candidates)

GradeMax.

markA B C D E


Mark scaled 60 41 36 32 27 23


Mark scaled 30 26 23 20 17 14



PA8P Turning Points in Physics Practical

(888 candidates)

GradeMax.

markA B C D E


Mark scaled 60 41 36 32 27 23


Mark scaled 30 23 21 19 17 15




48

PA9C Electronics Coursework

(249 candidates)

GradeMax.

markA B C D E


Mark scaled 60 44 39 35 30 27


Mark scaled 30 26 23 20 17 14



PA9P Electronics Practical

(160 candidates)

GradeMax.

markA B C D E


Mark scaled 60 44 39 35 30 27


Mark scaled 30 23 21 19 17 15




49

PA10 Synoptic Paper

(5601 candidates)

GradeMax.

markA B C D E



Advanced Subsidiary award

Provisional statistics for the award ( 6985 candidates)

A B C D E

Cumulative % 23.0 39.1 55.5 69.5 81.6

Advanced award

Provisional statistics for the award ( 5642 candidates)

A B C D E

Cumulative % 26.5 47.7 64.7 80.5 92.6

Definitions

Boundary Mark: the minimum mark required by a candidate to qualify for a given grade.

Mean Mark: is the sum of all candidates’ marks divided by the number of candidates. In order to

compare mean marks for different components, the mean mark (scaled) should be expressed as a

percentage of the maximum mark (scaled).

Standard Deviation: a measure of the spread of candidates’ marks. In most components,

approximately two-thirds of all candidates lie in a range of plus or minus one standard deviation from

the mean, and approximately 95% of all candidates lie in a range of plus or minus two standard

deviations from the mean. In order to compare the standard deviations for different components, the

standard deviation (scaled) should be expressed as a percentage of the maximum mark (scaled).

Uniform Mark: a score on a standard scale which indicates a candidate’s performance. The lowest

uniform mark for grade A is always 80% of the maximum uniform mark for the unit, similarly grade

B is 70%, grade C is 60%, grade D is 50% and grade E is 40%. A candidate’s total scaled mark for

each unit is converted to a uniform mark and the uniform marks for the units which count towards the

AS or A-level qualification are added in order to determine the candidate’s overall grade.

Documents

GCE 2003 June Series Report on the Examination GCE … 12,13/A level Physics pa… · · 2015-01-13June Series Report on the Examination Advanced Subsidiary – 5451 Advanced