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GCSE Standard Questions: The Motor Effect

Q1. A student investigates the electromagnetic force acting on a wire which carries an electric current. The wire is in a magnetic field. The diagram shows the circuit that the student uses.

(a) Draw an X on the diagram, with the centre of the X in the strongest part of the magnetic field.

Centre of the X midway between the poles

(1 mark)

(b) Give one change that she can make to the magnets to decrease the electromagnetic force on the wire.

Move the poles further apart OR use weaker magnets

(No mark is awarded for 'use smaller magnets' – size is not an indication of the strength - you can have small strong magnets and weak big ones!)

(1 mark)

(c) The student wants to change the electromagnetic force on the wire without changing the magnets or moving their position.

(i) Give one way in which she can increase the electromagnetic force.

Add more cells (to the battery) or reduce the resistance (of the variable resistor) accept increase the potential difference or voltage or current.

(1 mark)

(ii) Give one way in which she can reverse the direction of the electromagnetic force.

Reverse (the polarity of) the battery.

OR turn the battery or cells round OR swap the connections to the battery.

(1 mark)

(Total 4 marks)