Why does it become more difficult to pedal a bicycle-powered generator as

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lugnut87

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the load increases? A bicycle-powered generator is hooked up to a light bulb. The rider pedals the bike, lighting the bulb. A second bulb is added to the circuit, and it becomes harder to pedal. Why does this happen as opposed to having to pedal the bike faster?

Thanks!!!
Zargon -

Thank you! Hopefully I remember to come back and give you best answer for that.
 
Counter-intuitive, isn't it?

The reason is that with two light bulbs (in parallel) you decrease the electrical resistance in the circuit. As a result, when you turn the generator, more current flows. The force you are working against is the magnetic force caused by turning wires carrying current in a magnetic field. Since the wires have more current flowing in them, they generate more force when you turn them. When you remove all loads from the generator, current does not flow, and the magnetic force opposing your turning the rotor goes to practically nothing. All you feel is the mechanical friction.
 
i'm no expert here, but i would guess that if you increase the power of one bulb that would be true (increases speed), but adding quantity instead increases the difficulty.
 
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