An electric bulb rated for `500 W` at `100 V` is used in a circuit having a `200 V` supply. The reistance `R` that must be put in series with bulb, so that the bulb delivers `500 `W is ……….`Omega`.

Options

A. `10 Omega`
B. `20 Omega`
C. `50 Omega`
D. `100 Omega`

Answer

B

Explanation

(b) Reated current through the circuit `i= (500)/(100) = 5A`
Potential difference across `R , 100 = 5 xx R implies = 20 Omega`