# Water wheel for Physics Class?

I have to make a water wheel that lights up a 6volt bulb and it must have a switch so that when the water is pouring and the light turns on i can turn it of while it spins if i want. I don't know what materials i need or how to use them...HELP!

Jack A Lopez5 years ago
Honestly this sounds like kind of a challenging problem.

Is any part of this setup already built for you?  E.g. the water source?  The generator?

The amount of power available from falling water is just the mass flow rate times g (acceleration due to gravity) times h (the height it falls).

The amount of power needed to supply an electrical load is V*I,  voltage times current.

What I'm saying is to do these power calculations first to see if this is even practical.  Or at least figure out how many kg/s of falling water, or how far it has to fall.

Regarding generators, the tricky thing about building generators is that usually they have to turn very fast to produce significant amounts of voltage.  I am guessing this generator is essentially permanent magnets moving past coils of wire, so that the open circuit voltage is given by Faraday's Law, V = N*(dΦ/dt).  This equation suggests three ways to get more voltage from your generator.  (1) Make N bigger by using coils with more turns.  (2) Make Φ bigger by using more powerful permanent magnets. (3) Make (d/dt) bigger by increasing the speed at which the generator turns.

Because of this desire for speed, some sort of mechanical speed increasing trick,  like the "step up pulley" Rick suggested, may be necessary.

Because building a generator from scratch is somewhat tricky, it may be tempting to just find a motor containing permanent magnets, and drive it "backwards", or drive it as a generator
rickharris5 years ago
For 100;s of years water wheels have been built of wood. How much historic research have you done?

Wheel drives generator via step up pulley, generator drives lamp (via switch)