A 100 W bulb together with its power supply is suspended from a sensitive balance. Find the change in the mass recorded after the bulb remains on for 1 year .

Explanation

Given : Bulb is 100 Watt = 100J/s
So, 100 J is expended in 1 sec.
Hence total energy expended in 1 year
` = 100 xx 3600 xx 24 xx 365 `
` 315360000J`
Change in mass recorded ` Total energy / c^(2) = 315360000 / 9 xx 10^(16) `
` = 3.504 xx 10^(8) xx 10^(-16) kg `
` = 3.5 xx 10 ^(-8) kg `