An electric bulb, marked `40 W` and `200 V`, is used in a circuit of supply voltage `100 V`. Now its power is

Options

A. `10 W`
B. `20 W`
C. `40 W`
D. `100 W`

Answer

A

Explanation

Power of bulb is given by
`P = (V^(2))/(R )`
Supply voltage is `100V` and actual volatge is `200 V`
`:. (P_(1))/(P_(2)) = (V_(1)^(2))/(V_(2)^(2))`
`rArr (40)/(P_(2)) = ((200)^(2))/((100)^(2))`
`rArr P_(2) = (40)/(4) = 10W`