Question

Which of the following uses more energy, a 250W TV set in 2 h, or a 1000 W heater in 30 minutes?

Answer 1

We know
Power = Energy/time
Energy = power $\times$ time
Energy used by 250 W TV set in 2 h = 250 W $\times$ 2 h = 500 Wh

Energy used by 1000 W heater in 30 mins. (i.e., $\frac{1}{2}$ h)
= 1000 W $\times$ ($\frac{1}{2}$) h = 500 Wh

Thus, both 250 W TV set in 2 hour and 1000 W toaster in 30 mins uses equal energy.