CAIE IGCSE Physics Electricity and Magnetism Questions

Practise charge, circuits, electrical quantities, magnetic fields, electromagnetic effects and induction through calculations, diagrams and explanations.

Covered syllabus points

4.1 Simple phenomena of magnetism 4.2.1 Electric charge 4.2.2 Electric current 4.2.3 Electromotive force and potential difference 4.2.4 Resistance 4.2.5 Electrical energy and electrical power 4.3.1 Circuit diagrams and circuit components 4.3.2 Series and parallel circuits 4.3.3 Action and use of circuit components 4.4 Electrical safety 4.5.1 Electromagnetic induction 4.5.2 The a.c. generator 4.5.3 Magnetic effect of a current 4.5.4 Force on a current-carrying conductor 4.5.5 The d.c. motor 4.5.6 The transformer

[Maximum number: 6]

This question is about the magnetic fields around bar magnets. Fig. 7.1 shows two positions used by a student doing an experiment.

Fig. 7.1

(a)

Fig. 7.2 shows a magnet, labelled magnet 1, placed on position 1.

Fig. 7.2

On Fig. 7.2, draw lines to show the pattern of the magnetic field produced by magnet 1. Place arrows on the lines to show the direction of the field.

[ 3 ]

(b)

Magnet 1 is removed from position 1. Fig. 7.3 shows another magnet, labelled magnet 2, placed on position 2.

Fig. 7.3

On Fig. 7.3, draw, at the right-hand end of position 1, a line with an arrow to show the direction of the magnetic field produced by magnet 2 .

[ 1 ]

(c)

Fig. 7.4 shows magnet 1 placed on position 1 and magnet 2 placed on position 2.

Fig. 7.4

[ 2 ]

(i)

State the direction of the force that the N pole of magnet 2 exerts on the N pole of magnet 1.

[ 1 ]

(ii)

Justify your answer to (c)(i).
[Total: 6]

[ 1 ]

[Maximum number: 6]

A lightning conductor protects a tall building and the people in it against damage and injury caused by lightning strikes.

The lightning conductor is a very long strip of copper that is attached to the side of the building. At the top of the building, the strip of copper is connected to a vertical metal pole and at the bottom of the building, it is buried in the ground.

Fig. 7.1

The bottom of the thundercloud is negatively charged.
As the cloud moves closer to the building, the top of the metal pole becomes charged.

(a)

State the sign of the charge at the top of the metal pole. Explain, in terms of the particles involved, how it becomes charged.

[ 2 ]

(b)

As the cloud passes over the building, a lightning strike occurs and a charge of 0.84 C flows through the lightning conductor. The charge flows for $3.5 \times 10^{-5} \mathrm{~s}$ .

[ 3 ]

(i)

Calculate the average current in the lightning conductor during this time.

[ 2 ]

( I= ) $Q \div t$ or $0.84 \div 3.5 \times 10^{-5}$

C1

$2.4 \times 10^{4} \mathrm{~A}$

A1

(ii)

It is suggested that the current in the lightning conductor could be measured by connecting a laboratory ammeter between the pole and the copper strip.

State one reason why this cannot be successful.

[ 1 ]

(c)

The copper strip has a large cross-sectional area.

State how increasing the cross-sectional area of the copper strip affects its resistance.

[ 1 ]

[Maximum number: 7]

(a)

State what is meant by

[ 2 ]

(i)

an electric field,

[ 1 ]

(ii)

the direction of an electric field at a point.

[ 1 ]

(b)

Fig. 11.1 shows a positively charged sphere.

Fig. 11.1

On Fig. 11.1, draw the pattern of the electric field in the region around the positively charged sphere. Show the direction of the field with arrows.

[ 2 ]

(c)

The charge on the sphere in (b) is $+2.0 \times 10^{-5} \mathrm{C}$ . A high resistance wire is now connected between the sphere and earth. It takes 20 minutes for the sphere to become completely discharged through the wire.

[ 3 ]

(i)

Suggest why there is a current in the wire between the sphere and earth.

[ 1 ]

(ii)

Calculate the average current in the wire between the sphere and earth.

average current =

[ 2 ]

I=Q / t in any form OR Q/t OR $20 \times 10^{-6} /(20 \times 60)$ $1.7 \times 10^{-8} \mathrm{~A}$
OR
I=Q / t in any form OR Q/t OR $20 /(20 \times 60)$ $0.017 \mu \mathrm{~A}$
C1
A1
(C1)
(A1)
Total:

[Maximum number: 7]

A washing machine has an electric motor and an electric heater. Fig. 7.1 shows a simplified circuit diagram for the washing machine.

Fig. 7.1

The heater has a resistance of $25 \Omega$ and the power supply has an electromotive force (e.m.f.) of 230 V .

(a)

State the meaning of electromotive force.

[ 2 ]

(b)

State the potential difference (p.d.) across the heater.

p.d. =

[ 1 ]

(c)

Calculate the current in the heater.

Current =

[ 2 ]

(d)

The current in the motor is 1.6 A .

Determine the reading on the ammeter in Fig. 7.1. Explain your answer.

Ammeter reading
Explanation

[ 2 ]

(ammeter reading = ) $\{1.6+$ candidate's answer to 7(c) $\} \mathrm{A}$

B1

Sum of currents into a junction = sum of currents out of junction OR total current is sum of the current in the branches owtte

B1

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Covered syllabus points

4. Electricity and magnetism question 1

Question (a)

Question (b)

Question (c)

Question (i)

Question (ii)

4. Electricity and magnetism question 2

Question (a)

Question (b)

Question (i)

Question (ii)

Question (c)

4. Electricity and magnetism question 3

Question (a)

Question (i)

Question (ii)

Question (b)

Question (c)

Question (i)

Question (ii)

4. Electricity and magnetism question 4

Question (a)

Question (b)

Question (c)

Question (d)