IGCSEPhysicsCIETopic Questions4. Electricity & Magnetism4.3 Electric Circuits & Electrical Safety

Electric Circuits & Electrical Safety (CIE IGCSE Physics)

Topic Questions

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1a1 mark

A student makes a circuit to switch on a 6.0 V lamp from two different switches X and Y.

circuit6
Fig. 9.1 shows the circuit.

Switch X is in position P. State the position of switch Y for the lamp to be lit.

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1b4 marks

The current in the lamp is 0.50 A when the potential difference (p.d.) across the lamp is 6.0 V.

 
Calculate the resistance of the lamp. Include the unit.

  
  
resistance = ......................................................... 

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1c2 marks

The student connects another 6.0 V lamp in parallel with the first lamp, as shown in Fig. 9.2.

circuit7

Give two advantages of connecting the lamps in parallel.

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2a4 marks

A student investigates the electrical resistance of some components.

Fig. 10.1 shows an incomplete diagram of the circuit used by the student.

cie-2020-31-16

 
(i)
State the term used for component Y.
[1]
 
(ii)
The student uses the circuit to measure the resistance of component Y.
 
Complete the diagram in Fig. 10.1 by adding electrical symbols to show an ammeter and a voltmeter correctly connected to determine the resistance of component Y.
[3]

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2b2 marks

Fig. 10.2 shows two resistors A and B. 

 

cie-2020-31-17

 

(i)
Resistor A and resistor B are connected in series.
  
State the value of their combined resistance.
............................................ Ω [1]
 
(ii)

Resistor A and resistor B are connected in parallel.

 

Compare the combined resistance when in parallel with the resistance of resistor A alone.

[1]

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3a1 mark

Fig. 10.1 shows a circuit for determining the resistance of a component.

q10

On Fig. 10.1, label the fixed resistor, by writing the letter R.

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3b4 marks

Two components in Fig. 10.1 measure electrical quantities.

Identify the quantity that each component measures.

Write each quantity and the unit of each quantity in the correct place in Table 10.1.

bC_atcRu_q10b

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3c2 marks

A student uses the circuit in Fig. 10.1 to determine the resistance of wires made from the same material.

State how the resistance of a wire is related to its length and its diameter.

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4a2 marks

Fig. 9.1 and Fig. 9.2 each show an electrical circuit. Each circuit has two lamps connected to an electrical supply.

cie-2019-13

State the term used to describe each electrical circuit. Write the term under each circuit.

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4b2 marks

State two disadvantages of the circuit in Fig. 9.2.

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4c2 marks

Redraw the circuit in Fig. 9.1 with switches that will turn lamps X and Y on and off independently of each other.

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4d3 marks

Fig. 9.3 shows another circuit.

cie-2019-14

The lamps can be turned on and off using two different switches S1 and S2.

 

Complete the table stating when the lamps are on or off. The first one has been done for you.

switch positions lamps on or off
S1 S2
K Z off
K W  
J W  
J Z  

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5a1 mark
Fig. 10.1 shows the symbol for an electrical component.
screenshot-2022-10-27-at-16-40-38

State the name of the component shown in Fig. 10.1.

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5b4 marks

The resistance of the component shown in Fig. 10.1 varies with temperature. Fig. 10.2 shows a graph of resistance against temperature for the component.

screenshot-2022-10-27-at-16-42-47

(i)
Use the graph to determine the resistance of the component at a temperature of 10 °C.
  
  
resistance = ...................................................... Ω [1]
 
(ii)
At another temperature, the resistance of the component is 800 Ω.
   
Calculate the current in the component when it is connected to a 12.0 V supply.
  
  
current = ...................................................... A [3]

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5c2 marks

The students who built the circuit in part (a) want to change it so that it becomes sensitive to light rather than heat.

State the change the students should make.

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5d1 mark

Draw the symbol for the replacement component you suggested in part (c).

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1a4 marks

Fig. 11.1 shows lamps in series. Fig. 11.2 shows lamps in parallel.

The lamps are all identical 6.0 V lamps. In each circuit there are three ammeters A1, A2 and A3.

circuit3

(i)
Compare the readings on ammeters A1, A2 and A3 in Fig. 11.1.

[1]

 

(ii)
Compare the readings on ammeters A1, A2 and A3 in Fig. 11.2.
 
[1]

(ii)
State two advantages of connecting the 6.0 V lamps in parallel with the 6.0 V battery, compared with connecting the lamps in series with the battery.
 
[2]

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1b2 marks

Each lamp has a resistance of 12 Ω.

  
(ii)
Determine the combined resistance of the two lamps connected in series.
 
resistance = .................................................... Ω [1]
 
(ii)
Compare the resistance of one lamp with the combined resistance of the two lamps in parallel.
[1]

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2a3 marks

Fig. 8.1 shows a circuit.

circuit4

The lamp has a resistance of 3.0 Ω. Line XY represents a uniform resistance wire of resistance 6.0 Ω.

    

Calculate the reading on the ammeter.

 
 
ammeter reading = ........................................................ 

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2b4 marks

Fig. 8.2 shows the circuit with a different connection to the resistance wire and an added resistor. The length XY of the whole resistance wire is 2.0 m. The contact is made at Q where the distance XQ is 0.60 m.

circuit5

Calculate the resistance of the circuit.

  
  
resistance = ........................................................

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3a1 mark

A teacher demonstrates the action of a device. Fig. 10.1 shows the symbol for the device.

Oiv~c30B_thermistorState the name of this device.

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3b5 marks

Extended

Fig. 10.2 shows another device being used in a circuit. The circuit contains a 6.0 V lamp.

circuit8
(i)
The sliding contact of this device is at position A, as shown in Fig. 10.2.
   
Describe and explain the brightness of the lamp when the sliding contact is in this position.
[2]
   
(ii)
The teacher moves the sliding contact from position A to position B. Describe and explain what happens to the brightness of the lamp.
[2]
 
(iii)
The teacher moves the sliding contact from position B to position C. Suggest what happens to the lamp.
[1]

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4a2 marks

Fig. 8.1 shows a circuit that contains a battery of electromotive force (e.m.f.) 6.0 V, an ammeter, a 20 Ω resistor and component X.

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(i)
State the name of component X.
[1]
 
(ii)
The potential difference (p.d.) across the 20 Ω resistor is measured with a voltmeter.
 
On Fig. 8.1, draw the symbol for this voltmeter connected to the circuit.
[1]

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4b3 marks

Extended

The p.d. across the 20 Ω resistor is varied from zero to 6.0 V. For each value of p.d. a corresponding current is measured.

On Fig. 8.2, draw a line to indicate how the current measured by the ammeter depends on the p.d. across the 20 Ω resistor.

 

N~gQvqHE_q8b

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4c2 marks

A second resistor is connected into the circuit in parallel with the 20 Ω resistor.

 
(i)

State how the combined resistance of the two resistors in parallel compares with the resistance of each of the resistors on its own.

[1]

 

(ii)

The p.d. across the two parallel resistors is changed and the current in the battery for each value of the p.d. is measured. A second line could be drawn on Fig. 8.2 to indicate how the current measured by the ammeter depends on the p.d. across the two resistors in parallel.

State how the second line differs from the original line. You are not expected to draw this second line.

[1]

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5a3 marks

Extended

The circuit shown in Fig. 1 includes three ammeters labelled A1, A2 and A3, and one unknown fixed resistor, R.

The voltmeter connected across R reads 24 V

4-3-5a-h-parallel-series-circuit

For the parallel branch determine

            
(i)
The voltage across the upper 10 Ω resistor.
[2]
(ii)
The voltage across the lower part of the parallel circuit.
[1]

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5b2 marks

Calculate the current through the upper 10 Ω resistor.

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5c4 marks

Extended

Calculate the current in the circuit.

   
(i)
Determine the reading on ammeter A2.
[2]
(ii)
Determine the reading on ammeters A1 and A3.
[2]

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5d1 mark

Calculate the value of R.

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1a4 marks

Fig. 10.1 shows an arrangement for making an electromagnet.

circuit2

(i)
State a material which is suitable for the core of the electromagnet.

[1]

 

(ii)
State the name for component X in Fig. 10.1.
 [1]

 

(iii)
Describe and explain how component X varies the strength of the electromagnet.
 [2]

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1b3 marks

The switch is closed. The reading on the ammeter is 1.5 A.

 
Calculate the resistance of the circuit.

 
 
 
 
resistance = .................................................... Ω 

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2a8 marks

A student does an experiment to determine the resistance of a fixed resistor, R.
The student draws an incomplete diagram of the circuit, as shown in Fig. 10.1.

 

18p3-10a

(i)
On Fig. 10.1, draw the missing circuit symbols.
[3]
  
(ii)

Describe how the student could use the circuit to determine a reliable value for the resistance of R.

[5]

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2b4 marks

Fig. 10.2 shows a 20 Ω resistor connected to a power supply.

18p3-10b

A second 20 Ω resistor is connected in series with the first.

State and explain how this affects the current in the circuit.

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3a6 marks

A teacher is investigating the resistance of a lamp.


Fig. 10.1 shows part of the circuit she uses. The circuit is incomplete.

screenshot-2022-10-14-at-09-21-44

(i)
To determine the resistance of the lamp, the teacher adds two meters to her circuit.

On Fig. 10.1, draw circuit symbols to show each meter correctly connected in the circuit.

[3]

 

(ii)
When the current in the lamp is 0.25A, the potential difference (p.d.) across the lamp is 4.5 V. Calculate the resistance of the lamp.
 
 
 
resistance = ...................................................... Ω [3]

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3b3 marks
(i)
State the name of component X.

[1]

(ii)
Describe and explain how the teacher uses component X to investigate the resistance of the lamp.

[2]

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4a4 marks

A teacher uses a power supply in a metal case. The circuit for the power supply includes a fuse.

(i)
Draw the electrical symbol for a fuse.
[1]
 
(ii)

The metal case of the power supply is earthed. A fault occurs and a live wire touches the metal case.

 

Explain how earthing the metal case protects the teacher.

[3]

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4b3 marks

The power supply circuit includes a transformer. Its input voltage is 240 V. There are 960 turns on the input coil and 64 turns on the output coil.

Calculate the output voltage of the transformer.

 
 
output voltage = ..................................................... V 

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5a3 marks
A circuit is made from two lamps, a cell and a switch, as shown in Fig. 10.1.
screenshot-2022-10-20-at-11-18-35
(i)
Draw the circuit symbol for a cell.
[1]
 
(ii)
State the term used for the arrangement of lamps in the circuit in Fig. 10.1.
[1]
 
(iii)
The switch is closed and the lamps light.
   
State the name of the charged particles that are flowing through the wires.
[1]

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5b5 marks

Fig. 10.2 represents a different type of circuit.

screenshot-2022-10-20-at-11-40-21
(i)
Compare Fig. 10.1 and Fig. 10.2. State two advantages of the type of circuit shown in Fig. 10.2 with the type of circuit shown in Fig. 10.1.
[2]
  
(ii)
The potential difference across the power source in Fig. 10.2 is 3.0 V. The combined resistance of the two lamps is 12 Ω. Calculate the size of the current in the circuit when the switches are closed.
 
 
  
current = ...................................................... A [3]

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