Re: What is the thing like a bike that when u pedall the light turns on?

Actually, both the bike light and the thing you are talking about are two 
different manifestations of the exactly same thing:  they're both 
generators.  The bike light is a low voltage light that is turned by the 
bike wheel; the faster the wheel runs, the faster the shaft on the bike 
light runs and the higher the bike generator output voltage and current 
are.  The thing that you pedal (or, where I live, crank by hand) is also 
the shaft of a generator.  The faster you crank (or pedal) the more power 
you put out.  About the only difference between the bike and the pedalling 
machine is that the machine probably has an internal relay that only turns 
the light on when you reach a certain minimum cranking speed.  OK, so what 
happens to the power you generate when you're cranking the thing too 
slowly?  The power is routed either to a light bulb you don't see or 
perhaps a bank of dummy resistors;  either dissipates the power and the 
fundamental laws of the universe (thermodynamics) are not violated.  Hope 
this helps.