Suspended from a sensitive balance is a 100 W bulb along with its power supply. Determine the change in the recorded mass after the bulb is kept on for 1 year .

Step-by-step solution

The energy radiated by the bulb in one year is given by E = P t . Substituting the given values: P = 100 W t = 1 year = 365 24 60 60 s = 3.1536 10^7 s E = 100 3.1536 10^7 = 3.1536 10^9 J According to the mass-energy equivalence principle, the energy leaving the system as light and heat results in a decrease in the mass of the system. m = E c^2 m = 3.1536 10^9 (3 10^8)^2 m = 3.1536 10^9 9 10¹⁶ m = 0.3504 10⁻⁷ kg 3.5 10⁻⁸ kg