Electrical Circuits 1 Lecture Prelims

7/28/2019 Electrical Circuits 1 Lecture Prelims

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ELECTRICAL CIRCUITS 1 LECTURE PRELIMINARY EXAMINATION

1

NAME: __________________________ DATE: ______________

COURSE & YEAR: _______________ TIME: ______________

1. In the circuit below, the voltmeter has a resistance 100 k. The battery has negligible internalresistance and emf 6 V.

The reading on the voltmeter is

A. 0 V.

B. 2 V.

C. 3 V.

D. 4 V. (1)

2. Which graph best represents the relationship between the current Iand the voltage Vof a filamentlamp.

(1)

3. Three resistors P, Q and R, are each labeled 100 . They are connected as shown.

A. V

0

B. V

00 I 0 I

C. V

0

D. V

00 I 0 I


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The total resistance, when measured between points X and Y, is found to be 200 .

What is the correct explanation for the resistance reading?

A. Resistor R is zero

B. Resistor R is infinite

C. Resistor P is zero

D. Resistor P is infinite(1)

4. The work done on a positive point charge of magnitude 3.0 nC as it is moved at constant speedfrom one point to another is 12 nJ. The potential difference between the two points is

A. 0.0 V. C. 4.0 V

B. 0.25 V. D. 36V(1)

5. In the circuit below, resistors X, Y and Z are connected in series with a 9.0 V supply.

Resistors X and Z are fixed resistors of resistance 3000. The resistance of resistor Y may be

varied between zero and 3000 .

Which of the following gives the maximum range of potential difference Vacross the resistors Xand Y?

A. 0 to 6.0 V B. 3.0 V to 6.0 V

C. 4.5 V to 6.0 V D. 4.5 V to 9.0 V(1)

X

R

Y

Q

P

0

X Y Z

+9.0 V

3000 3000

V


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6. A resistor of resistance 1.0 is connected in series with a battery. The current in the circuit is 2.0A.

The resistor is now replaced by a resistor of resistance of 4.0 . The current in this circuit is 1.0 A.

The best estimate for the internal resistance of the battery is

A. 1.0. C. 4.0 .

B. 2.0. D. 5.0 .(1)

7. The graph below shows the variation with potential difference Vof the currentIin an electricalcomponent.

Which one of the following is a correct statement about the resistance of the component?

A. For potential differences greater than V0, the resistance is constant.

B. For potential differences greater than V0, the resistance decreases with increasing potential

difference.

C. The variation of current with potential difference is linear and so Ohms law is obeyed.

D. For potential differences less than V0, the resistance is zero.

(1)

8. A conductor of constant resistance dissipates 6.0 W of power when the potential difference across itis 12 V. The power that will be dissipated in this conductor when the potential difference across it is24 V is

A. 6.0 W. C. 24 W

2.0 A

1.0

A

4.0

I

0

0 V0 V


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B. 12 W. D. 48 W(1)

9. This question is about electrical resistance.

(a) Define electrical resistance.

...................................................................................................................................

...................................................................................................................................

(Total 2 marks)

10. This question is about an electric circuit

A particular filament lamp is rated at 12 V, 6.0 mA. It just lights when the potential differenceacross the filament is 6.0 V.

A student sets up an electric circuit to measure theI-Vcharacteristics of the filament lamp.

In the circuit, shown below, the student has connected the voltmeter and the ammeter into thecircuit incorrectly.

The battery has emf 12 V and negligible internal resistance. The ammeter has negligible resistance

and the resistance of the voltmeter is 100 k.

The maximum resistance of the variable resistor is 15 .

(a) Explain, without doing any calculations, whether there is a position of the slider S at whichthe lamp will be lit.

...................................................................................................................................

...................................................................................................................................

...................................................................................................................................

...................................................................................................................................

...................................................................................................................................(3)

(b) Estimate the maximum reading of the ammeter.

...................................................................................................................................

...................................................................................................................................(2)

12V

A

100 kS

V


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(c) Complete the circuit diagram below showing the correct position of the voltmeter and of theammeter in order to determine theI-Vcharacteristics of the filament lamp.

(2)

(Total 7 marks)

11. Electric circuits

(a) The diagram below shows the circuit used to measure the current-voltage (I-V) characteristic

of an electrical component X.

On the diagram above,

(i) label the ammeter A and the voltmeter V.(1)

(ii) mark the position of the contact of the potentiometer that will produce a reading ofzero on the voltmeter. Label this position P.

(1)

(b) The graph below shows the current-voltage (I-V) characteristics of two different conductors

X and Y.

12V

X


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(i) State the value of the current for which the resistance of X is the same as the resistanceof Y and determine the value of this resistance

Current: .....................................................................................................

Resistance: .....................................................................................................(2)

(ii) Describe and suggest an explanation for theI-Vcharacteristic of conductor Y.

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................(3)

(c) The two conductors X and Y are connected in series with a cell of negligible internalresistance. The current in the conductors is 0.20 A.

Use the graph in (b) to determine

(i) the resistance of Y for this value of current;

.........................................................................................................................

0.50

0.45

0.40

0.35

0.30

0.25

0.20

0.15

0.10

0.05

0.00

15.014.013.012.011.010.09.08.07.06.05.04.03.02.01.00.0

YX

I/ A

V/ V


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.........................................................................................................................(1)

(ii) the emf of the cell.

.........................................................................................................................

.........................................................................................................................(2)

(Total 10 marks)

12. This question is about electric circuits.

(a) (i) Define emf and state Ohms law.

emf: ....................................................................................................

....................................................................................................

Ohms law: ....................................................................................................

....................................................................................................(2)

(ii) The graph below shows theI-Vcharacteristic of a particular electrical component.

State show the resistance of the component is determined from the graph.

.........................................................................................................................

.........................................................................................................................(1)

(b) In the circuit below an electrical device (load) is connected in series with a cell of emf 2.5 V

and internal resistance r. The currentIin the circuit is 0.10 A.

00

V

I


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The power dissipated in the load is 0.23 W.

Calculate

(i) the total power of the cell;

.........................................................................................................................

.........................................................................................................................

(2)

(ii) the resistance of the load;

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................(2)

(iii) the internal resistance rof the cell.

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................(2)

(c) A second identical cell is connected into the circuit in (b) as shown below.

The current in this circuit is 0.15 A. Deduce that the load is a non-ohmic device.

load

I= 0.10A

e.m.f. = 2.5V

r

load

I= 0.15A


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...................................................................................................................................

...................................................................................................................................

...................................................................................................................................

...................................................................................................................................(5)

(Total 14 marks)

13.Determine the values of R1, R2, R3, and R4 for the voltage divider of Figure below if the source current is16 mA.

R1 = .............

R2 = .............

R3 = .............

R4 = .............

(Total 8 marks)

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Electrical Circuits 1 Lecture Prelims