Topic Menu

Cyber-chess a chess instruction site

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.

The north pole of the floating magnet is repelled from the north pole of the fixed magnet, so it moves away, but it is attracted to the south pole of the fixed magnet and therefore moves towards it.

[2 marks]

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

What happened to the piece of iron?

It was attracted to the fixed magnet and becomes magnetised.

[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.

 

This type of question is marked in two ways:

- the examiner looks for relevant points

- but also for a logical sequence...

It is not just a 'tick fest' - but a marker does look to see how many relevant points you have made, then considers how you have strung them together to put your answer into a 'level'

Level 2:

The design/plan would lead to the production of a valid outcome.

All key steps are identified and logically sequenced.
3 - 4 marks
Level 1:

The design/plan would not lead to a valid outcome.

Some relevant steps are identified, but links are not made clear.
1 - 2 marks
Level 0:

No relevant information
0 marks

 

Examples of indicative content that should be made in the response:

mark where the compass points on the paper

move the compass to the marked point

repeat until you go back to the magnet • join up the points

add an arrow pointing from the north pole to the south pole

repeat for positions (above and below the bar magnet)

[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.

elastic potential energy = 0.5 × spring constant × (extension)2

Ee = kx2

Ee = 0.5 x 200 x 0.0402

Ee = 0.16 J

[3 marks]

(TOTAL 12 marks)