A filament bulb `(500 W, 100 V)` is to be used in a `230 V` main supply. When a resistance `R` is connected in series, it works perfectly and the bulb consumers `500 W`. The value of `R` is

Options

A. `230Omega`
B. `46Omega`
C. `26Omega`
D. `13Omega`

Answer

C

Explanation

`P=(V^(2))/(R)`
`R_(b)=(V^(2))/(P)=(10000)/(500)=20Omega`

`i=(100)/(R_(b))=(130)/(R)`
`(100)/(20)=(130)/(R)`
`R=26Omega`