Two wire `A` and `B` of same meterial and mass have their lengths in the rato:. On connecting them to the same source, rate of heat dissiapted in `B` is found to be `5 W`. The rete of the heat dissipated is `A` is

Options

A. `10 W`
B. `5 W`
C. `20 W`
D. None fo these

Answer

C

Explanation

(c ) `(H)/(t) = P = (V^(2))/(R ) implies P prop (1)/(R )` also `R prop (l)/(A) prop (l^(2) rho)/(A l rho)` also
`implies R prop (i^(2))/(m) implies R prop l^(2)` (for same mass)
So `(P_(A))/(P_(B)) = (l_(B)^(2))/(l_(A)^(2)) = (4)/(1) implies P_(A) = 20 W`