Originally Posted by ilgoldstein

Got to thinking about Ohms Law again. I'm trying to figure out if I'm missing something here.

The light bulb is rated in watts at a certain voltage, isn't it? The resistance of the bulb (as measured by an ohm meter for example) is a constant.

See http://www.ac.wwu.edu/~vawter/Physic...esistOhms.html


So if P = I E, and P=100w, E = 120v, then I = .83A

E = I R, and R is constant (139.5). so double the voltage, same load, you double the current. At 240v, same R, I = 1.66A

So P = 240v x 1.66A = almost 400w.