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GCSE Standard Questions: The Motor Effect

Q5. The diagram below shows a loudspeaker made by Lex. When there is a current in the coil the paper cone moves.

Lex used the loudspeaker to investigate how changing the size of the current in the coil of wire affects the distance moved by the paper cone.

(a) State two variables Lex should control.

Any two from:

The number of turns on the coil OR how tightly the turns are wrapped.

You did not get a mark if you said 'number of coils' - the coil has turns of wire on it. Do not call them 'coils' - that is the whole object of coiled turns of wire!

The strength of the magnet OR distance between the magnet and coil/cone.

Both of the above affect the strength of the fixed magnetic field acting upon the coil.

The (stiffness/strength/elasticity/tension of the) elastic bands.

[2 marks]

(b) The results of the his investigation are shown in the graph below.

(i) When the current increases from 0.5 A to 0.9 A, how much does the distance moved increase?

2.7cm - 1.4 cm = 1.3 cm

[2 marks]

(ii) State two conclusions Lex can make from the graph.

Any two from:

(Below 1A) as the current increases the distance increases

Above 1A the distance does not change (with current) as the maximum distance (that the cone can move) is 2.8 cm

Between 0.3A and 0.7A (between 0.6 cm and 2.2 cm) the relationship is linear

References to 'positive correlation' and 'direct proportionality' were ignored, and a description of the shape of the graph (eg the line levels off after 1A) was insufficient to get you a mark

[2 marks]

(Total 6 marks)