An incandescent lamp consumint `P=54W` is immersed into a transparent calorimeter containing `V=10^3cm^3` of water in 420 s the water is heated by `4^@C`. The percentage of the energy consumed by the lamp that passes out of the calorimeter in the form of radiant energy is

Options

A. `81.5%`
B. `26%`
C. `40.5%`
D. `51.5%`

Answer

B

Explanation

Power sent to heat the water in the calorimeter
`P'=(ms Delta theta)/(t)`
`=(V rho s Delta theta)/(t)=(10^3xx10^-6xx10^3xx4200xx4)/(420)=40W`
Required ratio
`=(P-P')/(P)=(54-40)/(54)=(14)/(54)=26%`