P3.3

Question 1

What is produced when a current flows through a wire?

Answer 1

A magnetic field around the wire

Question 2

How could you make the magnetic field around a wire stronger?

Answer 2

~ Add an iron core
~ Have more current
~ Have more coils

Question 3

How do appliances using an electromagnet work?

Answer 3

~ Switch on circuit 1
~ The electromagnet carries a current 
~ Magnet switched on
~ Armature attracted 
~ Second circuit switched on

Question 4

A low current circuit can be used to do what?

Answer 4

Switch on a high current circuit

Question 5

How does a circuit breaker work?

Answer 5

If there is a large current the electromagnetic will be attracted to the electromagnet and the circuit will break

Question 6

What frequency do switch mode transformers work on?

Answer 6

50kHz to 200kHz

Question 7

What are switch mode transformers like and what are they used for?

Answer 7

~ Much lighter and smaller than transformers working from the mains
~ Use very little power when on with nothing connected
~ Used for mobile phone chargers

Question 8

How can the force of the moving wire be increased?

Answer 8

~ By increasing the current (more cells)

~ By increasing the strength of the magnetic field (stronger magnets)

Question 9

How can the direction of the moving wire be reversed?

Answer 9

~ By reversing the magnetic field (sides of north and south)

~ By reversing the cell which reverses the current

Question 10

How does the primary coil generate an alternating current in the secondary coil?

Answer 10

~ Insulated wires carry an alternating current in the primary coil
~ This produces a changing magnetic field in the iron core which produces a magnetic field in the secondary coil
~ This generates an alternating potential difference across the secondary coil and so an alternating current is produced in the secondary coil