A 100-W light bulb is turned on. It has an operating voltage of 120 V.

Question

A 100-W light bulb is turned on. It has an operating voltage of 120 V.

a) how much current flows through the bulb?

b) what is the resistance of the bulb?

c) how much energy is used each second?

Answer 1

a) Because W = V·I, where I is current, I = ·W/V = 100W/120V = 0.833 A

b) We have I = V/R, from here resistant R = V/I = V²/W = (120V)²/100W = 144 Ω

c) Enerdy A = W·t = 100 W ·1sec = 100 J