# Generators resistance?

1. Aug 12, 2004

### bonna

I'am making some calulations on a product that i later will atemte to build, and i was wondering how you calulate the resistance of a generator !? The mechanical resistance, that is how big a force will i need to drive e.g a 6v generator?

All replays welcome
Bonna

2. Aug 12, 2004

### Chi Meson

The mechanical resistance of a generator changes as the the amount of electricity used changes. If you switch off all appliances, the mechanical resistance of an ideal (frictionless) generator goes to zero. If the thing usung the electricity is at a steady level of demand, the input "work" should remain constant.

Using the law of conservation of energy, you will need to know how many watts of power is being used by the thing you are powering. You will need to put in this many watts of power, plus about 40% more, into the generator (to overcome friction and heat loss). If the generator is a hand-crank, for instance, you can estimate the force required:

power= (force x distance)/ time so:

force = (the number of watts required) times (the time in seconds to turn the crank once)divided by (the circular distance in meters through one turn of the crank).

The force will be in Newtons. divide by 4.4 to get pounds.