magnetism - the Alternatir and dynamo

Question 1

what can the generator effect be used to generate?

Answer 1

alternating current and direct current

Question 2

what is an alternator?

Answer 2

a coil of wire rotating in a magnetic field. coil connected to 2 metal rings called commutators which allows current to pass out of the coil. potential difference produced when wire passes through magnetic field

Question 3

alternator graph: describe it?

Answer 3

a wave
wire on left hand side of circuit with arrow pointing down always connects onto ring A.
graph:
- maximum potential difference produced when is when the coil is horizontal. wire is seeping directly through magnetic field lines at fastest possible rate. left hand side (red) moving downwards and right moving up (orange).
- when coil is vertical, potential difference falls to zero because coil moving parallel to field. coil is not cutting through the magnetic field lines
- as coil continues moving round, get a potential difference again. however it has now reversed direction. due to 2 sides of coil nos moving in a different direction to before. red side moving up and orange side down.
- coil vertical = moving parallel to magnetic field. pd zero

Question 4

alternator: because the 2 sides of the coil are attached to 2 different rings,

Answer 4

an alternator produces an alternating potential difference and an alternating current

Question 5

what happens when we increase strength of magnetic field in an alternator?

Answer 5

we increase the size of the alternating current. also increase size of alternating current if we increase number of turns on the coil or increase area of coil.

Question 6

what happens when we increase rotation speed of coil in an alternator?

Answer 6

increase both size and frequency of alternating current if we

Question 7

what does a dynamo produce? key features of a dynamo?

Answer 7

direct current
features:
- has a split-ring commutator. this has 2 sides separated by a gap
- side of coil that is moving down is connected to part A of split ring commutator (left side). moving up is connected to side B

Question 8

how does a dynamo work?

Answer 8

• coil is cutting through magnetic field lines, a potential difference and current are induced
• when coil is vertical it is moving parallel to magnetic field so potential difference is zero
• when coil has moved around, red side moving up orange side down. side of coil moving down still attached to part A of split ring commutator + side moving uo connected to part B. due to this, direction of pd and current do not reverse when coil rotates. we have direct current

Question 9

dynamo graph?

Answer 9

• 2 peaks = full rotation of coil because each side of coil passes through magnetic field twice during each cycle of rotation, once passing down and once passing up