Two electric bulbs rated `25 W , 220 V and 100 W , 220 V` are connected in series across a `220 V` voltage source . The `25 W and 100 W` bulbs now draw `P_(1) and P_(2)` powers , respectively.

Options

A. ` P_(1) = 16 W`
B. ` P_(1) = 4 W`
C. ` P_(2) = 16 W`
D. ` P_(2) = 4 W`

Answer

A, D

Explanation

Let `V = 200 V and R_(1) and R_(2)` be the resistance of the `25 W and 100 W` bulbs.
`P_(1) = 25 = V^(2)//R_(1) = or R_(1) = V^(2)//25 and R_(2) = V^(2)//100 `
When the bulbs are joined in series, the current is
`I = ( V) / ( R_(1) + R_(2))`
Power in the `25 W` bulb is `R_(1)I^(2)` and in the `100 W` bulb is `R_(2)I^(2)`.