Magnets

Question 1

Explain the difference between permanent and induced magnet.

Answer 1

A permanent magnet produces its own magnetic field

An induced magnet only becomes magnetised when placed in a magnetic field

Question 2

How can we increase the strength of a magnetic field?

Answer 2

Increase current

Increase turns in a solenoid

Add iron core

Question 3

Explain how you could determine whether a metal bar is permanent or induced.

Answer 3

If metal bar is permanent, it can be attracted to and repelled by the bar magnet.

If it’s induced, it will only ever be attracted to the bar magnet

Question 4

Explain the purpose of split ring commutator.

Answer 4

Reverses direction of current through a coil every half cycle

This reverses direction of force exerted on each side of coil

This allows for continuous rotation of coil

Question 5

What is one way in which the force exerted on wire could be reversed.

Answer 5

Reverse current direction or reverse magnetic field direction

Question 6

What is an electromagnet?

Answer 6

A solenoid containing electro magnets

Question 7

Explain what happens when the ignition is closed.

Answer 7

Current flows through electromagnetic

This causes iron bar to move about the pivot

This pushes the bottom contact towards top one to complete circuit

This delivers current to motor and engine starts

Question 8

One reason why a relay switch must be used in a car ignition circuit

Answer 8

Protects driver from dangerously high current

Question 9

Explain what will happen when a non permanent paper clip was removed and brought to the South Pole of a permanent magnet.

Answer 9

Paper clip still attracted to magnet because it is induced