If a `30 V, 90 W` bulb is to be worked on a `120 V` line, resistance of how many ohms should be connected in series with the bulb

Options

A. `10 ohm`
B. `20 ohm`
C. `30 ohm`
D. `40 ohm`

Answer

C

Explanation

(c ) Suppose resistance `R` is corrected in series with bulb.
Current through the bulb `i= (90)/(30) = 3A`
Hence for resistance `V = iR`
`implies 90 xx 3 xx R implies R = 30 Omega`