Prior knowledge - newmarketacademy.co.uk€¦ · Web viewElectrons that cannot move are called static charge. The word ‘static’ means ‘does move’. If enough static charge

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Year 7 Topic 3b: Electricity (Physics Mastery)

Contents Contents.........................................................................................................................2Prior knowledge..............................................................................................................31. Charge........................................................................................................................4

Structure of atom........................................................................................................5Electrons can be moved..............................................................................................7Current electricity (charge flowing).............................................................................9Conductors..................................................................................................................9Insulators (poor conductors)......................................................................................10Static charge.............................................................................................................11

2. Potential difference (Pd)...........................................................................................16What is potential difference?.....................................................................................16Power source e.g. battery..........................................................................................17Pd across other components.....................................................................................18

Measuring potential difference using a voltmeter ............................................193. Current – charges flowing.........................................................................................21

What is current?........................................................................................................21Current around a circuit............................................................................................22

Measuring current using an ammeter ..............................................................224. Resistance – tries to stop charge moving.................................................................23

The relationship between potential difference, resistance and current....................26Power............................................................................................................................27Models of electricity.....................................................................................................28Circuit Symbols and diagrams......................................................................................30Building circuits from diagrams....................................................................................31Series circuits...............................................................................................................33Parallel circuits.............................................................................................................35

Two types of current: AC and DC ....................................................................39Mains electricity (AC).................................................................................................42Climate change and the greenhouse effect...............................................................43National grid..............................................................................................................43Safety in the home....................................................................................................44

Earth wiring .......................................................................................................45Colour coding of wires............................................................................................45Fuses ...........................................................................................................46

Knowledge Organiser Questions...................................................................................47

Prior knowledge 1. What are the two types of charge?

a) Positive b) Up and c) Left and d) North and e) Yes and no2

and negative

down right south

2. What do we call charge that cannot move?a) Current b) Static c) Electrons d) Insulators e) Resistance

3. These materials have delocalised electrons (they can move)?a) Non-metals b) Metals c) Insulators d) Resistance e) Mixtures

4. Materials that are bad conductors are called?a) Semi-

conductorsb) Non-

metalsc) Metals d) Insulators e) Wires

5. This is needed to provide the energy for charge to move?a) Resistance b) Current c) Electrons d) Potential

differencee) Power

6. This tries to stop charge moving?a) Resistance b) Current c) Electrons d) Potential

differencee) Power

7. The rate of movement (or flow) of charge is called….a) Resistance b) Current c) Electrons d) Potential

differencee) Power

8. This is measured in Ohms (Ω)?a) Resistance b) Current c) Electrons d) Potential

differencee) Power

9. The amount of energy transferred by a device in one second?a) Resistance b) Current c) Electrons d) Potential

differencee) Power

10. Measured in Watts (W)?a) Resistance b) Current c) Electrons d) Potential

differencee) Power

11. The network of transformers, cables and pylons that connects power stations to our homes is called?a) Transfor

merb) Alternating

currentc) Parallel

circuitd) Network e) National

Grid12. A circuit where current has a choice of loops?

a) Series b) Parallel c) Complete d) Safe e) Short circuit

13. A circuit where current has only one loop it can follow?a) Series b) Parallel c) Complete d) Safe e) Short

circuit14. The circuit symbol for a resistor?

a) b) c) d) e)15. The circuit symbol for a battery?

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a) b) c) d) e)ReflectionBefore the topic End of the topic Score: /

15What were you pleased with? What were you pleased with?

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1. Charge Charge is a fundamental property of the Universe. There are two types of charge: Positive. Sometimes written as + or +’ve. Protons are positive

(+1 charge). Negative. Sometimes written as – or –‘ve. Electrons are negative

(-1 charge).Objects that have no charge are called neutral. Neutral. No charge or, equal amounts of positive and negative

charge. Neutrons are neutral (charge of 0).All atoms are neutral as they have the same number of protons as electrons.

Charges have non-contact forces between them. We call these electrostatic forces:

Opposite charges attract

Like charges repel16. What are the two types of charge?17. What does repel mean?18. Complete this table saying if each would attract, repel or neither.

Attract, repel or neither?


Two negative charges

Two neutrons

Two neutral charges

Two electrons

Electron and a proton

A proton and neutron

Atom and a neutron

Two atoms of Helium

A + ion and a – ion

O2- and F- ions

N3- and Mg2+ ions K+ and Cl- ions19. An ion of Sodium can be written as Na+. What does the + mean?20. An ion of Chlorine (Cl) has a charge of negative one. How might we write that in

symbol form?21. What would happen if you tried to push to electrons together? Why?

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22. Which of these forces are non-contact forces?a) Friction b) Weight c) Thrust d) Electrostati

ce) Magnetic

23. Which of these things can happen to an object if the forces acting on it are not balanced?a) Change shape b) Change

directionc) Change speed d) Change colour

24. Which of these things can happen during acceleration?a) Change shape b) Change

directionc) Change speed d) Change colour

25. What are the units of force? Why is it important to write them using a capital letter?

Structure of atom Here is an atom of Boron ( B511 ).

The protons and neutrons are buried deep in the nucleus. This means they are very difficult to move.Electrons are very small and on the outside of an atom. This means it is possible to move them. Most electricity we deal with involves electrons moving.When you see the word ‘electricity’ think of ‘electrons’.

The name electron was first used by the Irish Physicist George Johnstone Stoney in 1894. He almost called them ‘electrolions’. The word electron is a combination of electric and ion. The suffix -on was later used to name the proton and neutron when they were discovered.

26. Complete this diagram of a Lithium atom ( Li37 ). Add as much information as you

can.

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27. Why do protons not usually move?28. Complete this table comparing neutrons, protons, and electrons

Location in atom Mass ChargeNeutronProtonElectron

29. What sub-atomic particle should we always think of when we hear the word electricity?

30. Describe the types of electrostatic forces between the following:a) Neutrons and protons b) Protons and protons c) Protons and electronsd) Electrons and

electronse) Neutrons and

electronsf) Neutrons and neutrons

31. This student has made some errors. Can you correct them?

Scraping electrons off: the Van der Graaf generatorYour teacher will show you this demonstration.

We can use many things to demonstrate the repulsion force between negative charges such as:

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Beryllium has the symbol ( Be49 ). It is in Group 2 of the periodic table. It has 4 electrons

on its outer shell and 9 protons in the nucleus. There are 13 neutrons in the nucleus as well (4+9). The nucleus is neutrally charged because of the neutrons. The neutrons attract the electrons to stop them flying away.

A stack of metallic cake cups on top of the metal bell A long-haired doll on top of the metal bell Safety: Teachers, please read CLEAPSS guidance GL190 before

this demonstration.32. What force moves electrons off the belt and onto the dome of the Van der Graaf

generator?33. Why are electrons so much easier to move than protons?34. Complete this table comparing neutrons, protons, and electrons

Name of sub-atomic particle

Location in atom

Mass Charge

In nucleus +1Almost 0

35. What force causes electrons to jump off the Van der Graaf dome as a spark of mini-lightning?

Electrons can be moved When electrons are moved we say that charge is moved. Different atoms have electrons that move more or less easily than others depending on their structure. Boron is in Group 3 of the Periodic Table and Period 2. This means it has 3 electrons in its outer shell and 2 shells in total.

Remember: all atoms want stable (full or empty) outer shells. The number of electrons that can fill each shell is 2, 8, 8.Conductors: Metals (and Boron) have outer electrons shells with 1, 2 or 3 electrons. This means that it is easiest for them to lose those electrons rather than gain enough to have 8. Metals have delocalised electrons and are good conductors.

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Insulators: Non-metal atoms in Periods 1-4 and Groups 5-0 have full or nearly full outer shells. This means it is easier to gain electrons to get full outer shells. They do not have delocalised electrons and so are poor conductors. Poor conductors are called insulators.Group 4 atoms and Hydrogen are peculiar as they are half-way between full and empty shells. This means they sometimes behave like metals and conduct (e.g. graphite) and sometimes behave like non-metals and insulate (e.g. diamond). Diamond and graphite are both forms (allotropes) of carbon.

36. Gallium ( Ga3170 ) is in Group 3, Period 4.

a) Is Gallium a metal or a non-metal?b) How many electrons will Gallium have in its outer shell?c) How many protons will Gallium have in its nucleus?

37. Describe each picture below using the correct terms: ‘mixture of atoms’, ‘mixture of molecule elements’ or ‘mixture of compounds’ or ‘mixture of elements and compounds’.

a) b) c) d)38. Are there more metals or non-metals in the periodic table?39. Draw diagrams of the following atoms. Include the correct number of neutrons,

protons and electrons.Support a) Fluorine b) Lithium c) HydrogenFind in it in periodic table.

F919 Li3

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Chemical symbol, Group and Period

Group 7Period 2

Group 1Period 2

Draw nucleus.

Atomic mass = everything in nucleus.

19 Label protons.

Atomic number =number of protons in nucleus

9 Draw electron shells.

Period number = number of electron shells

2

Draw electrons on 7 9

outer shell.

Group number = electrons in outer shell

Fill inner shells.

Add electrons on full inner shells (2, 8, 8)

d) Neon e) Carbon f) Oxygen g) Nitrogen

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Current electricity (charge flowing) Current electricity is usually just called current. It happens when electrons or other charged particles flow.Conductors allow current to flow easily.We also use the word current to describe the flow of water and air. No current means no movement.

In 1780, Luigi Galvani was helping his wife prepare frogs leg soup (a delicacy in Bologna, Italy). He noticed that as her knife touched the dead frog’s leg muscle, it twitched. Galvani went on to identify that muscles could be made to twitch by electrical currents passing through them. We call this field of science bioelectromagnetics and it has led to many medical advances.

40. Compare air and electrical current. Use this visual organiser to help.

Conductors Conductors allow current to flow through them All metals are conductors. As they have delocalised (free)

electrons. Copper is used in electrical cables, gold is used in some music systems.

Graphite is a non-metal conductor made from carbon. It has delocalised electrons.

Salt water is a conductor. Sea salt is sodium chloride and is made of +’ve sodium ions and –‘ve chlorine ions. Ions are atoms that have lost or gained electrons and so have a charge. If these ions are in a liquid or a gas then they can move.

Our bodies use electrolytes (liquids with ions in) to conduct small currents.

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Insulators (poor conductors) Insulators do not allow electrons to flow through them. They are bad conductors. Most non-metals – do not have delocalised electrons. Gases – particles are too far apart Vacuums such as Space – no particles so no electrons or

charged particles41. What is the difference between a conductor and an insulator?42. Which charged particles usually move in an electrical current?43. Which of the following are conductors and which are insulators? Say why for

each?a) Gold b) Sea water c) Space d) Air e) Woodf) Plastic g) Graphite h) Diamond i) Mercury j) Copper

44. Complete this table comparing neutrons, protons, and electronsLocation in atom Mass Charge

NeutronProtonElectron

Conductor or insulator investigationWe are going to build a simple electrical circuit with a gap in it. The gap means that electrical current cannot flow through the circuit. Circuits with insulator gaps (like air) are called broken or incomplete.By putting different objects made of different materials in the gap we will see if those materials are conductors or insulators.

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45. What sub-atomic particle usually moves when we think about electricity?46. What is the difference between a conductor and an insulator?47. Why are metals such good conductors?48. Complete this table saying if each would attract, repel or neither.



Atom and a neutron Two atoms of Helium

Electron and a proton

A proton and neutron

N3- and Mg2+ ions K+ and Cl- ionsA +’ve ion and a –‘ve ion

O2- and F- ions

49. These atoms have lost or gained electrons to become ions. Join the ion to the correct charge.Hydrogen lost 1 electron

-3 O2-

Fluorine gained 1 electron

-2 Chlorine loses 1 electron

Magnesium lost 2 electrons

-1 Calcium in Group 2

Sr2+ +1

Nitrogen in Group 5

Bromine in Group 1 +2

Lithium in Group 1

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Static charge Static charge is charge that does not move (as a current). It happens when two insulators are scrapped against each other.When electrons are scrapped onto an insulator (poor conductor) they cannot flow.Electrons that cannot move are called static charge. The word ‘static’ means ‘does move’. If enough static charge builds up (enough electrons are scrapped on/off) then they will jump as a spark. When they jump they are going to Earth. Earth acts as the other end of a giant battery. Electrons will take the easiest path possible to reach Earth.We see and hear static sparks as lightning or when we take off a woolly jumper.This excellent simulation demonstrates how objects gain and lose static charge: https://tinyurl.com/99emwp6

50. What is the difference between static and current electricity?51. What acts as the other end of a giant battery that electrons try to get to?52. Why are metals such good conductors?53. This student has made some mistakes. Correct as many as you can.

54. How many electrons do atoms want in their first shell? How many in their second and third?

55. Complete this diagram of a Beryllium atom ( Be49 ). Add as much information as

you can.

56. What group must Beryllium be in?57. Why do protons not usually move?58. Why would wearing rubber boots help you avoid getting struck by lightning?59. Look at the KO Questions. Practice Look, Read, Cover, Write, Check for 5

minutes. Then work with your partner and test each other for another 5 minutes. 14

Most of the atoms in the Periodic Table are insulators. Insulators are poor conductors. This means that their protons flow easily as a current. Most non-metals are insulators and make -’ve ions by losing protons.

Write a list of the 5Q numbers you are most confident with. Write another list with the 5Q you are least confident with.

Investigating static chargeFriction is a contact force that tries to stop objects sliding past each other. We can use friction to scrape electrons off one object onto another. This will give make one object –‘ve charge (too many electrons) and the give the other +’ve charge (not enough electrons).

Use the structure strip below to write your method to test it.60. Hypothesis

being tested? (simple statement stating a relationship)

The longer we rub the polythene rod, the more charged it becomes

61. Independent variable (you change)

62. Dependent variable (you will measure )

Number of pieces of paper picked up

63. 3 control variables (ensures only the IV affects the DV – makes it fair)

1)

2)

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Do not pick same measuring device (ruler) 3)

69. Step by step method (start each line with a command verb e.g. measure, set-up, record)

1)

2)

3)

4)

5)

6)

81. Risk assessment(3 most obvious hazards in your experiment and how you will reduce their risk)

1)

2)

3)

87. Complete the investigation and record your results here

Time rubbed (s)

Number of pieces of paper picked up

Test 1 Test 2 Test 3 Average

2

4

6

1088. Are there any anomalous results in your table (ones that do not fit the pattern)?

How can you tell? If you have some put a circle around them. We will ignore these results from now on. Pretend they don’t exist.

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89. Calculate the mean average value for Average Number of pieces of paper for each time rubbed rowUsing mean = (1st test + 2nd test + 3rd test) ÷ 3 Remember to ignore anomalies e.g. If 2nd test result is anomalous then mean = (1st

test + 3rd test) ÷ 290. Complete the axis titles for your investigation on the graph below.91. Plot your average number of pieces of paper results below.

92. Are there any anomalous results in your graph (ones that do not fit the pattern)? How can you tell? If you have some put a circle around them. We will ignore these results from now on. Pretend they don’t exist.

93. Draw a line of best fit for your graph. Ignore any anomalous results. If the points look like they’re in a straight line, use a ruler. If they look curved then a maximum of one bend. Do not connect dot-to-dot.

94. Look at the origin of your plotted graph. Origin means start point. Starting there and looking right, what happens to the line and its steepness. Use this to write your conclusion for your graph with this prompt:

As ‘the time rubbed’ increases, the number of pieces of paper’ increasesdecreases

stays the same. The steepness of the graph increases

decreasesstays the same so the rate of change also increases

decreasesstays the same .

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95. If the number of pieces of paper picked up increases the longer you rub the polythene, what must be happening to the charge on the polythene?

96. Use your graph and your line of best fit to predict how many pieces would be picked up if you rubbed the polythene rod for 8 seconds. Make sure you draw a line up from 8 on your graph and a line across where it hits the line of best fit.

97. Did this investigation support the hypothesis you were testing? (Look back at the hypothesis earlier)

98. Complete MultiChoice Questions Topic 7.1a. List 5Qs you are happy with and 5Qs you are not.

99. Extended writing challenge. You score points by using key words. You can use words more than once.The Hindenburg airship was a balloon filled with Hydrogen gas. Hydrogen has a very low density and is highly reactive with oxygen. In 1937 the Hindenburg exploded killing all37 passengers.One theory is that as it travelled through the air it built up a static charge. This led to a spark jumping to the landing tower which caused the hydrogen to ignite.Use your science knowledge to explain what happened.

1 Point: Electrons Scrapped A particle model

comparing low and higher density gas

2 Points: Negative charged Combustion

reaction3 Points:

Exothermic reaction

Water

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2. Potential difference (Pd) What is potential difference?

Potential difference is a measure of the difference in energy between two parts of a circuit. The bigger the difference in energy, the bigger the potential difference.Potential difference is measured in Volts (V) and has the symbol V.It is sometimes referred to as voltage but this in not correct. We will always call it potential difference or pd.

Allessandro Giuseppe Antonio Anastasio Volta (1745-1827) was an Italian physicist who is credited as the inventor of the electric battery. His first battery was called the ‘voltaic pile’ which was initially made from wine goblets, filled with saltwater. In these he placed two different types of metals. Our modern batteries use a similar process and often contain zinc and manganese metals. The unit Volts is named after him so it is important we always use a capital letter.

100. What does pd stand for?101. What are the units of potential difference? Why must they always have a capital

letter?102. Why are metals such good conductors?103. This student has made some mistakes. Correct as many as you can.

104. Name the sub-atomic particle that normally flows as electrical current? What is its charge and mass?

105. Look at the KO Questions. Practice Look, Read, Cover, Write, Check for 5 minutes. Then work with your partner and test each other for another 5 minutes. Write a list of the 5Q numbers you are most confident with. Write another list with the 5Q you are least confident with.

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The voltage of an electrical current tells us the speed that electrons move. It is measured in volts (v).

Power source e.g. battery For charge to move there has to be a potential difference.In a normal circuit, a battery provides the potential difference for the charge to flow. The bigger the potential difference, the greater the rate of flow of charge.Here is a model of the potential difference provided by a battery. Imagine the ball is a lump of charge. The bigger the potential difference, the bigger more energy each charge is given by the battery.

Misconception 1: Some models incorrectly call the Potential Difference provided by the power source as a ‘push force’. Misconception 2: Some people think that the power source contains all of the charge and that these race around the circuit quickly. This is often reinforced by models for current such as lorries going around tracks. The electrons that move in a current are all around the circuit in the conductors. The power source transfers energy to ‘shunt’ them all along. Electrons in wires actually move quite slowly (a few cm/s) but since they are all so close together they move virtually as one.Misconception 3: It is an error to say that batteries run out of charge. When a battery stops working it is because it has run out of energy to move charge. We should really say ‘re-energising a battery’ rather than ‘recharging a battery’.

106. Which of these statements is true, which is false? Correct the false statements.a) Potential difference is

measured in vb) The greater the

potential difference the greater the rate of movement of charge

c) When we recharge our mobile phone, we put charge back in

d) Batteries provide energy for charge to move

e) Batteries provide the push force for electrons

f) Electrons in electric wires travel at the speed of light

107. Match-up the correct battery configuration to the correct total potential difference and reasonBattery arrangement Total potential

differenceReason

0 v Batteries

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arranged correctly

1.5 V Batteries reversed cancel each other out

3V

Pd across other components Devices such as bulbs, speakers and motors are called components. They transfer energy from the current to other stores of energy e.g. thermal store of the surroundings.This means that charge arrives at a component with more energy than they leave. Therefore, there must be a potential difference across components.All circuits have to allow charged particles to have a route all the way around a circuit. If they do not, then the circuit is broken and will not work.This means that the pd across all the components a charge passes through in a circuit must be equal to the pd it was given by the battery. The model below shows this. The energy each charge has at a point is shown the values in the diamonds .Energy is measured in Joules (J). We will look into energy in more detail in Year 8.

108. How much energy is transferred by each charge in the components below?a) 6V bulb b) 230V

cookerc) 2V

calculatord) 1.5V watch e) 12V battery

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109. A charge arrives at a lamp with and energy of 12J it leaves with an energy of 8J. How much energy has the charge transferred in the lamp? What is the potential difference across the lamp?

110. What is the potential difference of each of these devices?Energy of each charge before device

Energy of each charge after device

Energy transferred by each charge in device

Potential difference across device (V)

a) 12 4

b) 20 18

c) 6 6

111. A charge arrives at the first lamp with an energy of 12J it leaves with an energy of 6J. It then arrives at the next lamp and leaves with an energy of only 2J. How much energy has the charge transferred to both lamps in total? What is the potential difference across both lamps?

Measuring potential difference using a voltmeter The device we use to measure the potential difference is called a voltmeter. Each side of a voltmeter must be connected to each side of a component because it is measuring the difference in energy of charge before and after the component.When we build circuits, we always add the voltmeter last of all once we have tested the circuit is working.

Investigating potential differenceIn science lessons we use batteries or power packs to provide a potential difference. We do not often use mains electric. We do this because the current and potential difference from mains electric are too high and are dangerous.In this investigation we are going to find the typical potential difference in Volts of a selection of electrical power sources.

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112. Why are metals such good conductors?113. What charge and mass are electrons?114. What device do we use to measure potential difference?

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115. Record your results in the table belowObject Potential difference (V)

LemonBatteryPower packTwo batteries joined together

116. Why do we use power packs rather than lots of l emons when we use electricity in the lab?

117. Which of these Voltmeters is not set up correctly? Say why?

How a battery works Many batteries still work in the same way as Volta’s first

electrical cell developed in the late 1700s. They use an acid reacting with two different types of metals.

Acids have a pH of 1-6 and taste sour.Bases are the opposite of acids and have a pH of 8-14. A dissolved base is called an alkali. A substance that is neither acid or base is called neutral and has a pH of 7.

In the lemon battery it is citric acid reacting with copper and zinc. In larger batteries we often use sulfuric acid which people call battery acid.

Hydrochloric acid is the same acid found in our stomachs. We use it to kill microbes and help digestion.This is the word equation for an acid reacting with a metal.

Acid + Metal Metal salt + HydrogenA salt is a compound formed when an acid reacts with a base. It has the hydrogen in the acid replaced by the metal (usually) from the base. Sulfuric acid + Metal Metal Sulfide salts

e.g. Sulfuric acid + Lead Lead sulfide + Hydrogen

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Hydrochloric acid + Metal Metal Chloride saltse.g. Hydrochloric acid + Iron Iron chloride + Hydrogen

Citric acid makes citrate salts. In the lemon battery described earlier, the zinc nail reacted with the citric acid to make zinc citrate and hydrogen.

118. What pH are acids? What pH are bases?119. Draw the products of the reaction of hydrochloric acid + calcium calcium

chloride + Hydrogen

120. Why does the mass in the reaction above seem to go down?121. What happens to the battery when all the reactants have finished reacting122. Write word equations for these reactions:

a) Hydrochloric acid + Zinc b) Sulfuric acid + Magnesiumc) Sodium + Hydrochloride acid d) Lithium + Sulfuric acid

3. Current – charges flowing What is current?

If there is a potential difference and charge can move, then it will flow as currentCurrent is a measure of the rate at which charge flows. It has the symbol I as it was originally called ‘intensité du courant’ by its discoverer Andre-Marie Ampere.Current is measured in A, Amps or Amperes. All different names for the same thing.Since electrons are so small and are not the only things that have charge, we tend to talk about charge flowing rather than electrons. Current is often called the rate of flow of charge. This means the amount of charge that flows each second. Misconception: Many people wrongly think that current is speed of charge. It is not. Current is the total charge moved each second. A small quantity of charge moving fast may result in the same current as a large quantity of charge moving slowly.

123. Why is current given the symbol I and not C?25

124. What is current measured in? Why is it important to use a capital letter?125. Complete this table comparing neutrons, protons, and electrons


Current around a circuit The current that flows into any component must flow out. This is why all circuits must be made of complete, unbroken loops.Current can split at junctions if there is another route around a circuit but the law above must be obeyed. Circuits with more than one loop are called parallel circuits. Circuits with only one loop are called series circuits. We will look at both series and parallel circuits later in this topic.

Measuring current using an ammeter We measure current using an Ammeter. It only considers how quickly charge is flowing in one position.Resistance tries to stop current moving.

126. What are the units of current? Why do we use capital letters?127. What are the units of potential difference? Why do we use capital letters?128. If a battery has a potential difference of 0V, what size current can it cause?129. If 3A of current flow into a bulb, how much must flow out?130. If 4A of current flows into a junction and 1A goes one way, how much must go

the other?131. Why are metals such bad insulators?132. Complete MultiChoice Questions Topic 7.1b. List 5Qs you are happy with and

5Qs you are not.Demonstrating current using the inertia beads model

This is a model. Models are a way for scientists to simplify and explain things. This model uses a string of beads moving between two jars. The beads represent charge moving. The height difference between the two jars represents the potential difference. The rate of movement of the beads represents the current.

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133. What happens to the current through a device if we increase the potential difference across it?

134. Are there more metal or non-metal elements?135. How many electrons do atoms want in their 1st shell? How many in each of their

2nd and 3rd shells?136. Lithium is in Group 1 and Period 2 of the Periodic Table. Draw and label an atom

of Lithium Li37 .

137. Look at the KO Questions. Practice Look, Read, Cover, Write, Check for 5 minutes. Then work with your partner and test each other for another 5 minutes. Write a list of the 5Q numbers you are most confident with. Write another list with the 5Q you are least confident with.

138. Extended writing challenge. You score points by using key words. You can use words more than once.A newly discovered species of electric eel produces the highest potential difference of any known animal. Potential differences of up to 860V have been recorded. They produce it using specialised cells called electrocytes. These eels can grow up to 2m in length.Electric eels live in the freshwater of South America. They use the shock for defence against and catching prey such as small fish. Small fish feed on plants. Humans are some of the eels only predators.Describe a typical food chain involving an electric eel. Also describe how we might test an eel to see what potential difference it can generate.

1 Point: Producer Consumer

2 Points: Habitat Herbivore Voltmeter

3 Points: Energy flow Current Specialised

cells

4. Resistance – tries to stop charge moving The word ‘resistance’ means to ‘oppose something happening’. Think about resisting the urge to giggle, water-resistant clothing or, the French Resistance during the 2nd World War. Electrical resistance opposes charge moving. The higher the resistance, the more opposition to current there is.Conductors have low resistance but insulators have very high resistance.

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Resistance has the symbol R and is measured in Ohms (Ω)Resistance behaves like a friction force. It makes objects get hot by transferring energy into their thermal store. That is why all electrical devices get hot. It is caused by electrons trying to squeeze past the atoms, nuclei and other electrons inside the conductor. This is thought to be one reason why birds like sitting on electrical wires so much (warms them). It is also the reason snow melts more quickly on electric wires. (We will look into why birds do not get electric shocks later).

139. What does the word resistance mean?140. Which have lower resistance to electrical current, conductors or insulators?141. What are the units of current? Why is it important to use capital letters?

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142. Which statements below are true and which are false? Correct the false statements.

a) Current has the symbol I because it was called ‘intensité du courant’

b) Potential difference is the rate of flow of charge

c) High resistance means current flows easily

d) All electrical devices get hot because of resistance

143. Why are metals such good conductors?144. Complete MultiChoice Questions Topic 7.2a. List 5Qs you are happy with and

5Qs you are not.

George Simon Ohm (1789-1854) was a German Physicist and teacher. He experimented with Volta’s new battery and that the size of the current through a component depends upon the potential difference across it and its resistance.

Ohm discovered a mathematical relationship between the potential difference across a device, its resistance and the current through it. It is known as Ohm’s Law.Ohm’s Law: Current = Potential difference ÷ Resistance (I = V ÷ R)

Or rearranged as V = I RResistance of most metals increases when they get hot. This causes them to get even hotter and, in some cases, melt. This is how fuses work and why light bulbs tend to ‘blow’ when they are first switched on. We will look into fuses later in this topic.

145. Complete the questions below:a) What is the potential difference across a bulb with a current 3A and a

resistance of 6Ω?b) A resistor has a resistance of 10Ω and a current of 3A runs through it. What is

the potential difference it?c) A diode of 5Ω is connected in circuit with an ammeter and has a voltmeter

placed across it. The ammeter reads 4A. What does the voltmeter read?d) A battery manufacturer claims that their 12V battery can achieve a current of

3A in a circuit of up to 5Ω. Is this claim correct?e) When a thermistor is heated its resistance falls from 1000Ω to 100Ω. When

this happens the current rises from 2A to 10A. What happens to the pd across the thermistor as it heats up?

146. What are the units of electrical resistance?

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Investigating resistance using a modelThis is a simple model demonstrating the effect of resistance on current. It uses students to represent the current of moving charges. It uses marks on the floor as resistance.

Use the structure strip below to write your method.147. Hypothesis

being tested?The more resistance the lower the rate of flow of students


The number of marks students must stand on

149. Dependent variable (you measure)

Time taken for students to all go over marks

150. 3 control variables (ensures only the IV affects the DV – makes it fair)Do not pick same measuring device (ruler)

1)

2)

3)

156. Step by step method (start each line with a command verb e.g. measure, set-up, record)

1)

2)

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3)

4)

5)

6)

168. Complete the investigation and record your results hereNumber of

marksTime taken for students to all go over

marks (s)1234

169. How might you check to see if any of your results are anomalous?170. What should you do if you think one of your results are anomalous?171. What happens to the rate at which charge moves (current) as resistance

increases?The relationship between potential difference, resistance and current

These three items are the fundamental variables in electricity.

Insulators do not normally conduct as their resistance is so high. If the Oomph is big enough however i.e. if the potential difference is high enough even air will eventually allow a current to flow through it eg lightning.

172. One metre of air has a very high resistance (around 20 million billion Ω). Does this mean that lightening has a high or low potential difference?

173. Why are metals such good conductors?174. What are the units of electrical resistance?31

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Power Some objects transfer energy much quicker than others. The measure of how quickly energy is transferred is called Power.A bright bulb transfers more energy every second that a dim one.Power is measured in Watts (W). A 100W light bulb transfers more energy every second that a 10W bulb.The rate at which an electrical device transfers energy depends upon how many charges arrive at it every second and much energy each is carrying. The number of charges arriving is the current and the amount of energy each provided is the potential difference.We will look at power again in Year 8 as part of the Energy topic.Here is a model for the power of an electrical device.

175. What is power a measure of? What units does it have?176. What represents the current in the model above?177. What represents the potential difference in the model above?178. Calculate the power of each device below.

a) Current of 3A. Potential difference of 4V

b) A component in a circuit where V = 5V I = 2A.

c) Transfers 20J of energy each second

d) Takes 10 seconds to transfers 100J of energy.

e) In 3 seconds 18J of energy are transferred.

f) A component in a circuit where I = 3V I = 1.5A.

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179. What force is responsible for scrapping electrons off an atom and causing static electricity?

Models of electricity Electricity is a difficult concept to understand. Much of what makes it work is too small to see or imagine. Models help us to simplify and visualise difficult concepts but it is important to remember that each has its own strengths and weaknesses. Here are four popular models for electricity:

180. In the rope model what represents the charge? What happens when there is a pd of 0V?

181. In the rope model how and where can we observe the heating effect of a current?

182. Compare the rope model and the water in pipes model for electrical circuits.

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183. What is power a measure of? What units does it have?184. What are the units of electrical resistance?185. What is Ohm’s law relating current, potential difference and resistance?

186. What does the difference in height of the blocks represent in the lego model?187. In the lego model, how can you tell where the components are?188. In the human model, how can you tell that the cell is losing energy over time?189. What is current the rate of flow of?190. Which model do you feel best describes why the current before a component is

the same as after it?

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191. What is the difference between conductors and insulators?192. Of the models above, which do you prefer? Say why. 193. Compare the lego model and the human model for electrical circuits.

Circuit Symbols and diagrams When we draw circuits, we use symbols for components. We also always use straight lines for wires and draw them in rectangular patterns. This means that anyone can read them and makes them easier to build or analyse.There are six main shapes we use in circuit symbols. Each has a specific meaning. These shapes help us to create many of the symbols used in circuits.

194. How does the symbol for a cell give us a clue that it contains two types of wires?

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195. This student has made some mistakes in their circuit. Identify the mistakes and draw correct circuit.

196. What is power a measure of? What units does it have?197. What force is responsible for scrapping electrons off an atom and causing static

electricity?198. Why is I the symbol for?199. What are the units of potential difference? Why must we use a capital letter?200. What are the units of current? Why must we use a capital letter?201. What are the units of electrical resistance?202. What is Ohm’s law relating current, potential difference and resistance?

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n volts ( A

V

Building circuits from diagrams There are some simple rules to follow when you build circuits that will help you get them right first time, every time.1. Clear an area on your desk and collect all the components. Do

not get wires yet.2. Lay all the components out in the same pattern as the circuit

diagram.3. Now get some wires. Put two wires in voltmeter then move aside

– voltmeters always go last.4. Add wires between components. Work in loops starting at one

side of the battery and ending at the other side of the battery. 5. Test circuit. If there is a current, it is working. If there is not.

Check with teacher or check wires. Tie a knot in any faulty wires so no one else uses them.

6. Add voltmeter without removing any other wires.

Practice building circuitsFor each of these circuits practice using the 6 steps above to build them correctly. When you’ve finished one, ask your teacher to check then record the potential difference and current in the table below. Then dismantle it entirely and try the next.

Circuit Current at that position (Amps)

Potential difference (Volts)

1 – Series circuit (one loop)2 – Series circuit (one loop)3 – Series circuit (one loop)

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4 – Parallel circuit (more than one loop)

203. What do you notice about the current in circuit 1, 2 and 3 (the circuit with one loop)?

204. What do you notice about the pd across the battery in circuit 1 and the pd across both bulbs in circuit 3? Is this what you expected?

Practice drawing circuit diagramsConverting a real circuit into a diagram that can be easily read is an important skill. There are some rules that we always follow:1. Circuit symbols are always used.2. The cell/battery goes at the top of the diagram.3. Wires are always drawn straight lines using a ruler.4. Corners in wires are always at right angels (90o).5. Add voltmeters last.6. Start at one side of the cell/battery and work clockwise, one loop

at a time.205. Match the circuit to the correct circuit diagram

206. Use the 6 rules above to draw correct circuit diagrams for the circuits below.

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207. What is power a measure of? What units does it have?Series circuits

All circuits need at least one loop to work. This loop must connect one side of the battery (or cell or other power source) to the other side.Series circuits only have one loop. All current must go through every component. Important: We always ignore voltmeters here. They do not count as another loop.

Current in a series circuit: Current is the same through every component in series. This is because charge has only loop to follow.Potential difference in a series circuit:

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Potential difference is shared across components in series.

The potential difference combined for each component must equal the potential difference provided by the battery.

E.g. The battery gives each charge an 7J of energy. So the pd across the battery is 7V. Each charge must transfer some energy to each component it meets and come back to battery with none.

208. How many loops does a series circuit have?209. What do we call a circuit where the current has no choice of routes from one

side of the battery to the other?210. What are the units of current?211. What are the units of potential difference?212. What are the units of resistance?213. What does electrical resistance do?214. What is the Ohm’s Law equation that relates potential difference, current and

resistance?Current in a series circuit investigation

215. Build each of the circuits above in turn and record the current in the table below.

Circuit 1 Circuit 2 Circuit 3Current (Amps)

216. The current should be the same in each position. To what extent do your results support this?

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Potential difference in a series circuit investigation


Circuit 1 Circuit 2 Circuit 3 Circuit 4Potential difference (Volts)

218. The potential difference of the cell should be shared across each bulb. Do your results support this?

219. Calculate the power of each device below.a) Current of 3A.

Potential difference of 4V

b) A component in a circuit where V = 5V I = 2A.

c) Transfers 20J of energy each second

d) In 3 seconds 18J of energy are transferred.

Parallel circuits Parallel circuits have more than one loop. Each loop provides an alternative route from one side of the battery to the other.

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Current in a parallel circuit: Current is shared across each branch. This is because the charge splits up at each junction.Potential difference in a series circuit: Potential difference is the same across each whole

branch. Every charge does not go through every component so must

transfer their energy across the components they visit.

220. How many loops does a parallel circuit have?221. What happens to the current when it gets to a junction in the wires?222. If 10A arrive at a junction and 9A go down one path, how many must go down

the other?223. A wire has a 4A current and another has a 6A current. What is the current after

both wires join? 224. A bulb has a resistance of 6Ω and a current of 3A. What is the pd across it?

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Current in a parallel circuit investigation


Circuit 1 Circuit 2 Circuit 3 Circuit 4Current (Amps)

226. The current in a parallel circuit should be shared across each branch. Do your results support this?

Potential difference in a parallel circuit investigation

227. Build each of the circuits above in turn and record the potential difference in the table below.

Circuit 1 Circuit 2 Circuit 4Potential difference (Volts)

228. The pd in a parallel circuit should be the same across each branch. Do your results support this?

229. This student has made four mistakes. Identify the mistakes and draw a correct circuit diagram.

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Current in parallel circuits with components in seriesIn a parallel circuit the current has more than one loop from one side of cell to the other. In some parallel circuits, components are arranged in series on a branch. When components are in series, the current has to go through each one in turn.


Circuit 1 Circuit 2 Circuit 3 Circuit 4Current (Amps)

231. The current in circuits 3 and 4 is measured along the same branch. These two bulbs are in series with each other so the current should be the same. To what extent do your results support this?

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n volts ( A

V

232. The current in circuit 1 should be the most as it has not yet split. The current in circuit 1 should equal the currents in circuit 2 and 3 combined. Do your results support this?

233. Look at each circuit below. Circle the lights the switch could switch off.Circuit 1 Circuit 2 Circuit 3 Circuit 4

Switch would control

234. What is the Ohm’s Law equation that relates potential difference, current and resistance?

Potential difference in parallel circuits with components in seriesIn a parallel circuit the current has more than one loop from one side of cell to the other. In some parallel circuits, components are arranged in series on a branch. When components are in series, the current has to go through each one in turn.In a parallel circuit, the potential difference across each branch must be the same. It must be shared out across components on that branch if they are in series.

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235. Build each of the circuits above in turn and record the potential difference in the table below.

Circuit 1 Circuit 2 Circuit 3 Circuit 4 Circuit 5Potential difference (Volts)

236. The potential difference across the battery in circuit 1 should be the same as the potential differences across the bulb in Circuit 2 and the pair of bulbs in Circuit 5. Do your results support this?

237. The potential differences in circuit 1 should equal the pd from circuits 3 and 4 combined. Does it?

238. Complete this diagram of a Lithium atom ( Li37 ). Add as much information as you

can.

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239. Why do protons not usually move?240. Complete this table comparing neutrons, protons, and electrons


241. What sub-atomic particle should we always think of when we hear the word electricity?

Two types of current: AC and DC Static electricity does not move. Electrical current means that electrons are moving. The greater the current, the great the rate of flow of charge. It is measured in A, Amps or Amperes.Electrical devices work because charge moves. Many devices do not require the current to be in any particular direction so long as it is moving.There are two types of current electricity: alternating current and direct current (AC and DC).Current that only flows in one direction is called Direct Current or DC. Batteries and cells produce direct current. Direct current has this symbol . You will see it on battery

charging cables.Current that constantly swaps directions is called Alternating Current or AC. It is much easier to generate alternating current on large scales. Alternating current has this symbol . You will see in on any

mains electrical devices. The electricity we use in our homes is alternating current. It is

generated by huge generators spinning quickly hence the spinning/alternating nature of the current.

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The UK, mains electricity current changes direction 50 times each second (50Hz)

242. What is the difference between static electricity and current electricity?243. What type of current do batteries produce?244. Complete MultiChoice Questions Topic 7.2b. List 5Qs you are happy with and

5Qs you are not.245. Compare DC and AC below.

In the UK, nearly every mains-electrical device hums with a frequency of 50Hz. In the US, their electricity has a slightly higher frequency. This means that electrical devices hum with a little higher pitch in the US.

In the late 1800s a fierce rivalry known as the ‘War of the Currents’ was raging between Thomas Edison (iconic inventor of the light bulb) and Nikola Tesla.In one corner was Edison, rich and powerful who had a company producing direct current (DC) electricity. In the other corner was Tesla who felt that alternating current (AC) was easier to produce and more efficient. It was AC which eventually came out victorious although Tesla did not get the credit he deserved. Tesla also predicted the passing of information wirelessly using waves which we now take for granted.

246. How many times do electrons in UK mains electric change direction in 1 second?247. What are the units of potential difference?248. How many loops does a series circuit have?249. Why are metals such good conductors?

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Investigating using AC and DC

Use the structure strip following to plan key aspects of the investigation.250. Hypothesis being

tested? (simple statement stating a relationship)

The type of current affects the brightness of a bulb


252. Dependent variable (you will measure )

253. 3 control variables (ensures only the IV affects the DV – makes it fair)Do not pick same measuring device (ruler)

1)

2)

3)

Model of AC and DCThis model considers energy transferred via work done by a saw cutting wood rather than by moving charge. In each case there is movement which causes an effect. The final outcome is similar even though different movements were used. There is also energy transferred into the thermal store of the wood and surroundings (they get hot) which is similar to current.

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259. How does the model of cutting wood using a rotating circular saw model a direct current?

260. What type of current is produced by a battery?261. Which circuits below are series, which are parallel?

a)b)

c) d)

e) f) g) h)

Mains electricity (AC) In the UK our mains electricity comes from a number of different sources. But it all has two things in common:1. It is alternating current that switches direction 50 times each

second (frequency of 50Hz).2. It has potential difference of 230V.Power stations generate the majority of the electricity we use in our homes. They are enormous and are often hundreds of miles away from where we live. We will look at them more closely in Year 8.

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These huge cooling towers near Hull are releasing steam. Steam is water in gas form. When it cools to 100oC or less it will condense back into liquid water. 100oC is the boiling and cooling point of water. It is the temperature at which water (liquid) boils into steam (gas) or steam (gas) condenses in water (liquid). Water is a product of burning fuel. Burning is an exothermic reaction known as combustion.Combustion reaction: Fuel + Oxygen Carbon dioxide + Water

262. What is the potential difference of UK mains electricity?263. How many times does the current in UK mains electricity change direction each

second?264. Methane gas is a fuel used to generate electricity. It has the chemical equation

CH4. What is a molecule of CH4 made of?265. What are the products of the combustion reaction of methane (CH4) and oxygen

(O2)?266. Match these reactions and descriptions to the correct terms.

Combustion Gives off energy Exothermic

PhotosynthesisRespiration Takes in

energy EndothermicNeutralisation

267. Extended writing challenge. You score points by using key words. You can use words more than once.Arc welding uses high current to melt metal. This liquid metal then cools and freezes which we call a weld.It used in many places and the local company, TWI (The Welding Institute) work with welding around the world.Describe how arc welding works including information on what happens to the particles when they get hot and when they cool.

1 Point: Electrons Safety

2 Points: Potential

difference Particles vibrate

more3 Points:

Resistance Bonds get

weaker Freezing

Climate change and the greenhouse effect Global warming is a term for the Earth getting hotter over time.

We measure average annual temperatures and compare against previous years. There is a very strong body of evidence to suggest the Earth is warming.

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The greenhouse effect is the most agreed on theory for what is causing global warming. It suggests that Carbon Dioxide and other greenhouse gases are creating an insulating layer around Earth which prevent it from cooling as it should.Climate change describes the changing weather patterns which are happening due to global warming.

National grid The national grid is a network of transformers, pylons and cables (transmission lines) that transports electricity across the UK from power stations to our homes.

The national grid It is very similar to the road network except it moves electricity.

268. What is a typical potential difference of the cables hanging between giant electrical pylons?

269. What is the potential difference of UK main electric in our homes?Transformers increase or decrease the potential difference of the electricity in order to transport in more efficiently (waste less energy). Pylons hold electrical cables high off the ground. Here are some images of transformers and pylons.

270. What do electrical transformers do to the potential difference?271. Why do we want transformers to transport electricity more efficiently?272. What is the National Grid for?53

273. What is the National Grid made of?274. What are the units of current?Safety in the home

Mains electricity can be dangerous. An electric shock is when a current flows through our body. A mains electric shock can burn, affect breathing or affect heartrate. It can also cause falls, explosions and fires.In the home we use a number of different techniques to stay safe: Design: use of insulators, colour coding; earth wires, fuses, trip

switches Expert installation: only qualified electricians can work with

electricity Care: we switch devices off when not in use, we check for

damage; we use devices properly and with respect275. What is an electric shock?276. How might an electric spark cause an explosion?277. What sub-atomic particle do we think of when we see the term electricity?278. Match the following properties to the correct power supply.

Direct current Mains electric 230V

Alternative current An AA battery 1.5V

279. Look at each circuit below. If the switch was open, circle the lights that would be off.

Circuit 1 Circuit 2 Circuit 3 Circuit 4

Switch would control

280. What is the Ohm’s Law equation that relates potential difference, current and resistance?

Earth wiring For a current to flow it needs a complete circuit. This means it needs somewhere to go. If there is nowhere to go, then a current will not flow.Birds can sit on electric cables safely because there is nowhere for the current to go. This means that the current will not flow through them and they remain safe.

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When the potential difference is high (like mains 230V) then the current will flow into the Earth if it can get there. Earth contains metals and acts like the huge end of a battery. During lightning storms electrons jump from clouds down to Earth in fractions of a second.We use this knowledge to improve safety in our homes by adding ‘Earth wires’ to everything metal that is near mains electric. These green and yellow striped wires are attached to long poles that go deep into the ground. They act as safe routes for current to take instead of going through our bodies.

The symbol for electrical earth is .281. Why can birds sit on electrical cables without being electrocuted?282. What does the earth act like when current flows into it?283. What are earth wires in the home connected to?284. What colour are earth wires in the home?285. What jumps down to Earth during a lightning strike?Colour coding of wires

As well as the earth wire, we colour code the other two wires used in mains electricity. These two wires act as the main wires into and out of each device in the same way as our simple circuits. Live wire – Brown – this is the most dangerous wire Neutral wire – Blue – dangerous. Completes circuit when working

properly Earth wire – Green/Yellow stripes – to aid recognition by colour

blind people All wires are coated in plastic insulator.

286. Why do we cover all mains electric cables in plastic?287. Match these properties to the correct wire

Blue Live wire Safety wire

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Brown Neutral wire Very dangerous

Green and yellow stripes Earth wire

Dangerous completes normal

circuitFuses

The fuse is a resistor with a thin wire running through it. If the current gets too high, it gets hot and melts.Since the resistance of the earth wire is very low, any current running through it will always be high. This causes the fuse wire to get very hot and melt (or blow). This then creates a gap and breaks the circuit.The fuse is always attached to the brown live wire in a plug as this is the most dangerous.

288. How can we tell that a fuse is a type of resistor just by looking at the symbol?289. When a fuse blows, what has actually happened to it?290. Which wire in the plug is the fuse wire always attached to?291. What sub-atomic particles move in a normal electrical current?292. What is the difference between AC and DC electricity?293. What is the pd of UK mains electricity?294. What colour is the live wire?How a fuse works demonstration

Your teacher may demonstrate this practical. Students cannot complete themselves.As the potential difference increases so does the current through the constantan wire. This causes the temperature of the wire to increase. This is exactly how an old filament lamp bulb works. Eventually the wire gets so hot it melts and breaks the circuit. This is what a fuse does to keep us safe. It is known as ‘blowing a fuse’.

295. What happened to the wire as the current through it increased?296. What safety precautions did your teacher take?297.

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Knowledge Organiser Questions KQ.1. What are the two types of charge? Positive and negativeKQ.2. What is the charge of a neutron? NeutralKQ.3. What do call the negatively charged particle in an

atom?Electron

KQ.4. What charge is a proton? +1KQ.5. What do we call materials that do not let current

flow through them?Insulators

KQ.6. What do we call materials that allow current flow through them?

Conductors

KQ.7. Why are metals such good conductors? They have delocalised electrons

KQ.8. What force can scrape electrons off insulators? FrictionKQ.9. What are the units of potential difference? Volts or VKQ.10. What device do we use to measure potential

difference? Voltmeter KQ.11. What do we call the rate of flow of charge? CurrentKQ.12. What units do we measure current in? Amperes, Amps or AKQ.13. What device do we use to measure current? Ammeter

KQ.14. What symbol do we use to represent current? I

KQ.15. Why are non-metals such bad conductors They do not have delocalised electrons

KQ.16. What does electrical resistance do? Tries to stop currentKQ.17. What are the units of electrical resistance? Ohms or ΩKQ.18. What is the equation relating resistance,

current and potential difference?V = I R

KQ.19. What do we call the variable we measure in an investigation?

Dependent variable

KQ.20. What do we call the variable we change in an investigation?

Independent variable

KQ.21. What do we call the variables we keep the same so that only the independent variable affects the dependent variable?

Control variables

KQ.22. What do we call it when electrons jump through air?

Spark (or lightning)

KQ.23. This measures how quickly energy is transferred?

Power

KQ.24. The units of power? Watts (W)KQ.25. Draw the circuit symbol for a battery

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KQ.26. A circuit with only one loop? Series circuitKQ.27. A circuit with more than one loop? Parallel circuitKQ.28. What happens to current in a series circuit? It is the same all aroundKQ.29. What happens to current in a parallel circuit? It is shared across each

branchKQ.30. What happens to potential difference across

components in series?It is shared across them

KQ.31. What happens to potential difference across components in parallel?

It is the same across each

KQ.32. The number of protons in a Lithium ( Li37 ¿

atom?3

KQ.33. The number of neutrons in a Lithium ( Li37 ¿

atom?4

KQ.34. The number of electrons in a Lithium ( Li37 ¿

atom?3

KQ.35. What type of current do batteries produce? Direct currentKQ.36. What type of current is mains electric? Alternating currentKQ.37. What is the potential difference of mains

electricity?230V

KQ.38. When we build a circuit which measuring device do we always add last? Voltmeter

KQ.39. What greenhouse gas is given off when we burn fuels?

Carbon dioxide

KQ.40. What does the National Grid do? Move electricityKQ.41. What do we call the network of transformers,

pylons and cables?National Grid

KQ.42. What colour is the Earth wire in UK mains electric?

Green and yellow (striped)

KQ.43. When lightning strikes where do the electrons go?

Into Earth

KQ.44. What colour is the dangerous Live wire in UK mains electric?

Brown

KQ.45. What colour is the dangerous Neutral wire in UK mains electric?

Blue

KQ.46. Which wire is the most dangerous in UK mains electric?

Brown Live wire

KQ.47. Why do we cover electric cables in plastic? InsulatorKQ.48. What happens to a fuse when too much

current passes through it?Melts (and breaks circuit)

KQ.49. In the National Grid, what do electrical transformers do to potential difference?

Increase it or decrease it

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KQ.50. What two things might global warming lead to?

Climate change and rising sea levels

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Documents

Prior knowledge - newmarketacademy.co.uk€¦ · Web viewElectrons that cannot move are called static charge. The word ‘static’ means ‘does move’. If enough static charge