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Electricity · Chapter 3: Generators and AC

Year 11 Science · About 15 minutes with activities · Turn your sound on

Chapter 3 · Generators and AC
Current flips direction50 cycles every second
1 turn = 1 cycle of ACzero and reversing twice per turn
Moving down: current• out of the page
Moving up: reversed× into the page
No cutting: no currentstill, or parallel to the lines
Right hand onlyleft hand is for motors
Generator simulatordrag the coil and watch the graph
Coming in: repelnear end becomes N
Going out: attractnear end becomes S

Chapter 3 recap

  • AC periodically reverses direction and changes its magnitude continuously (graph: a wave; symbol: ~ with a line above). DC flows in a single direction at a steady size (flat line; solid line above a dashed line).
  • Moving a wire across field lines induces a current. Fleming’s right-hand rule: thumb = motion, first finger = field, second finger = current. Lenz’s law: the induced current opposes the change.
  • AC generator: a coil turns between magnets; slip rings + carbon brushes. Current is zero and reverses when the sides move parallel to the field (twice a turn). Faster = bigger, more frequent peaks.
  • Next: Chapter 4 · Transformers and the national grid

How does spinning a coil make the electricity in your wall socket?

Chapter 3 · About 15 minutes · sound on

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