4.7.3.2 Uses of the Generator Effect (HT only) Flashcards
1
Q
What is the generator effect used in?
A
- in alternator to generate ac
- in dynamo to generate dc
2
Q
How is the generator effect used in an alternator to generate ac?
A
- when the wire moves through the magnetic field the coil cuts magnetic field lines
- a p.d. is induced across the coil
- as there is a complete circuit a current is induced
- every half-turn the p.d. reverses direction
- so every half turn the current changes directions - alternating current
- as the 2 sides of the coil are attached to 2 different commutator rings an alternator produces an alternating p.d. and an alternating current (AC)
3
Q
What does a generator look like?
A
- coil of wire rotating in a magnetic field
- the coil is connected to 2 metal rings - commutators
- the commutators allow the current to pass out of the coil
4
Q
How does p.d. change in an alternator?
A
- when the coil is horizontal it is at maximum p.d.
- at this point, the wire is cutting directly through the magnetic field lines at the fastest possible rate
- when the coil is vertical p.d. falls to 0 in alternator
- as the coil is now parallel to the magnetic field so the coil is not cutting through the magnetic field lines
- p.d. is at lowest
- as coil continues moving round p.d. has reversed direction as the 2 sides of the coil moving in different direction to which they were previously moving in
5
Q
Factors to increase the size of the AC in an alternator:
A
- (stronger magnet) increase strength of magnetic field - induce stronger p.d
- increase number of turns on coil
- increase area of coil
- increase rotation speed of the coil - increases both the size and frequency of the alternating current
6
Q
Graph of p.d. generated in alternator:
A
7
Q
Diagram of alternator:
A
8
Q
How is the generator effect used in a dynamo to generate dc?
A
- has 1 split ring commutator - split ring commutator has 2 sides separated by a gap
- side of coil moving up is connected to 1 side of the split ring commutator and the side of the coil that is moving down is connected to the other side of the split-ring commutator
9
Q
How does p.d. change in a dynamo?
A
- coil horizontal
- as coil is cutting through the magnetic field lines a p.d. and current are induced
- coil vertical
- moving parallel to magnetic field
- not cutting through any field lines so p.d. is 0
- coil moved around
- direction which the sides of the coil are moving is opposite to the direction which they were previously moving
- the side of the coil moving down still connected to same side of split ring commutator
- side of coil moving up still connected to same side of split ring commutator
- so direction of p.d. and current does not reverse when coil rotates - d.c.
10
Q
Diagram of dynamo:
A
11
Q
Graph of p.d. generated in dynamo:
A
12
Q
Use of slip rings in alternator:
A
- provides continuous connection between coil and transformer
- stops wires twisting together
13
Q
Why does the handle of an alternator become much easier to turn when the alternator from the power supply becomes disconnected from transformer and lamp?
A
- no induced current
- no magnetic field
- to oppose movement of coil