Question

An electric bulb is rated at 220 V, 100 W. (a) what is its resistance? (b) what safe current can be passed through it?

Answer 1

(a) Given,

Power, p = 100 w
Voltage, v = 220 v
As power, P = `V^2/R`

                R = `(220)^2/100` = 484 Ω 

(b) The safe limit of current that can pass through it

I = `P/V` 

I = `100/220` =0.45 A