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GCSE Level Questions: Magnets and Electromagnets

Q6. (a) Antonio placed a magnet on top of a plastic support in a bowl of water.

This magnet was fixed in position and above the surface of the water. The student put a second magnet into a piece of cork so that the magnet floated on the water.

Only the north pole of the floating magnet was above the surface of the water.

This diagram shows the arrangement of the magnets:

(i) The floating magnet was placed near to the north pole of the fixed magnet. The floating magnet then moved along the path shown above.

Explain why.

[2 marks]

(ii) Antonio replaced the floating magnet with a piece of iron.

What happened to the piece of iron?

[1 mark]

(b) Describe how to use a compass to plot the magnetic field pattern around a bar magnet.

Use the diagram below to help you.

[4 marks]

(c) Here is a diagram of an electromagnetic lock used to secure a door.

The block diagram below shows an incomplete sequence of how the door unlocks:

Write one letter in each box to show the correct sequence.

A The iron bolt moves.
B A magnetic field is created around the solenoid.
C There is a current in the circuit.

[2 marks]

(d) The electromagnetic lock contains a spring.

When the door is unlocked the extension of the spring is 0.040 m.

If the spring constant = 200 N/m, calculate the elastic potential energy of the spring when the door is unlocked.

[3 marks]

(TOTAL 12 marks)