An electric bulb, when connected across a power supply of `220V`, consumes a power of `60 W`. If the supply drops to `180V` ,what will be the power consumed? If supply is suddenly increased to `240 V`, what will be the power consumed?

Answer

A, D

Explanation

`E = 220V`
`P= 60 W`
`, `R = (V^2)/(P)`
` `
`= 220xx(220)/(60) = 806.67 Omega`
` (a) `
`E' = 180V`
` P' = `
`(V^2)/(R ) = 40.16 =40 W`
` (b) `
`E'' =240V`
`P''= (V^2)/(R )`
`=71.4 W= 71W`.