4.7.3.1 Induced Potential (HT only)

Question 1

How is induced potential and induced current created?

Answer 1

• there is a magnetic field around the magnet
• move a wire /coil through a magnetic field this causes the magnetic field to change as the wire moves through the magnetic field line the wire cuts through the field lines
• so then a potential difference is induced through the end of the wire/coil
• when the wire stops moving then the p.d. is lost
• p.d. reverses direction when moved in and out of magnetic field
• if the circuit is complete then this induces a current - direction of current switches when the direction of movement switches (if movement stops current also stop)
• get induced potential and induced current if wire is kept still but move the magnetic field

Question 2

When can you only see the generator effect?

Answer 2

• only see the generator effect if wire passes through the magnetic field - cuts through field lines
• if wire moves along parallel the magnetic field then no p.d. or current is induced

Question 3

What happens when you move a magnet in and out of a coil in a complete circuit and how can you change the direction of the current?

Answer 3

• produces an induced current as circuit is complete
• the direction of the current changes when the direction of movement changes
• when moving magnet through the magnetic field of the coil can change the direction of the current if you switch the poles of the magnet

Question 4

What happens to the forces on a magnet when you move it in and out of a coil in a complete circuit?

Answer 4

• moving magnet into coil of wire
• causes p.d. to be induced as field lines being cut which causes current to be induced in the wire as circuit is complete
• wire creates its own magnetic field
• this magnetic field opposes the movement of the magnet
• e.g. when you push north pole of magnet into coil the same end of coil becomes a north pole which repels the magnet making it harder to push in + when pulling the north pole out of the coil that end of the coil becomes a south pole making it harder to pull out
• as the induced current makes it harder to move the magnet this means that work is being done
• so energy being transferred from movement of magnet to movement of current

Question 5

Generator effect:

Answer 5

• if an electrical conductor moves relative to a magnetic field or if there is a change in the magnetic field around a conductor
• a p.d. is induced across the ends of the conductor (due to field lines being cut)
• if the conductor is part of a complete circuit, a current is induced in the conductor

Question 6

Lenz’s law:

Answer 6

• an induced current generates a magnetic field that opposes the original change
• either the movement of the conductor or the change in magnetic field

Question 7

Factors that affect the size of the induced p.d./induced current:

Answer 7

• (stronger magnet) strength of magnetic field - large p.d. induced
• move the wire more rapidly through the magnetic field/move magnets more quickly - faster the magnetic field will change - will induce bigger p.d.
• shape the wire into a coil - the greater number of turns on the coil then the greater then induced p.d and induced current

Question 8

Factors which affect the direction of the induced p.d./induced current:

Answer 8

• change direction of movement of magnet/coil
• switching poles of the magnet