Generator

A generator is a motor working backwards. Turn a coil between two magnets and it makes electricity. Spin it faster and see what happens to the bulb.

Connected through
Voltage now
0.0 V
Peak voltage
0.0 V
Frequency
0.0 Hz
Bulb power (avg)
0.00 W

The maths, live

Angular speed ω = 2π × fω = 2π × 0.0 = 0.0 rad/s
Peak ε₀ = N × B × A × ωε₀ = 200 × 0.10 × 0.008 × 0.0 = 0.0 V
Now ε = ε₀ × sin(ωt)ε = 0.0 × sin 0° = 0.0 V
Bulb P = V² ÷ RP = 0.0² ÷ 12 = 0.00 W at the peak

Turn the coil twice as fast. What happens to the height of the wave and to how close together the waves are? Then switch to a split ring.

How it works

When a wire moves through a magnetic field, a voltage is made in it. This is called electromagnetic induction. A spinning coil cuts through the field fastest when it lies flat along the field, and not at all when it faces the field, so the voltage rises and falls as it turns: ε = N × B × A × ω × sin(ωt).

With slip rings, the voltage flips between positive and negative every half turn. This is alternating current (AC), the kind that comes out of the sockets at home. Spinning faster gives a higher voltage and more waves every second. More turns of wire or a stronger magnet also give a higher voltage. A split ring flips the connections so the current always flows the same way (DC).

Try this

  1. Double the speed. What happens to the peak voltage and to the frequency?
  2. Find the slowest speed that makes the bulb glow brightly.
  3. Switch to a split ring. How does the graph change?