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GCSE Standard Questions: The Motor Effect

Q6. Tommy did an investigation in class. The diagram below shows apparatus set up by Tommy.

(a)

(i) Explain why a force acts on the wire XY when the switch is closed.

Closing the switch makes a current flow through the wire. When a current flows a magnetic field is created around the wire. This field interacts with the permanent magnetic field around the magnet.

Just saying the wire attracts/repels the magnet is insufficient to get you a mark. You need to talk about the two magnetic fields interacting with each other.

[3 marks]

(ii) The force causes the wire XY to move. Draw an arrow on the diagram to show the direction in which the wire XY will move.

The wire will move upwards - you need to use Fleming's Left Hand Motor Rule. See the diagram.

[1 mark]

(iii) State the effect that this experiment demonstrates.

The motor or catapult effect

[1 mark]

(b) Tommy replaces the battery with a low frequency alternating current (a.c.) power supply. He then closed the switch.

(i) Describe the movement of the wire.

The wire moves up and down or the wire vibrates

[1 mark]

(ii) Give a reason for your answer to part (i)

The force changes direction (from upwards to downwards, on the wire) because the direction of the current in the wire is changing direction and this means that the direction of the magnetic field of the wire changes too.

[1 mark]

(Total 7 marks)