Chapter 19
Electromagnetic induction
A changing magnetic field through a circuit can induce an e.m.f.
Spaced review
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Producing an induced voltage
Use observations to identify a changing magnetic field and the factors affecting induced e.m.f.
The direction opposes the change
Find induced poles and current directions for a magnet approaching or leaving a closed coil.
A simple a.c. generator
Trace the slip-ring connections and relate coil orientation to a voltage-time graph.
How transformers change voltage
Explain magnetic coupling and calculate voltages, turns and currents in an ideal transformer.
Reducing transmission losses
Keep useful power fixed and distinguish cable voltage drop from load voltage when calculating heating losses.