Question

How much energy is required to run a 35 W light bulb for 4.0 min?

Answer 1

P = 35 W

t = 4.0 min = $\frac{4}{60}$ = 0.066 h

$E = P \times t$

$E = 35 \times 0.066 = 2.33\; Watt\;hour = 2.33 \times 10^{-3} \; kW\;h$

Proportion:

1 kW-h – $3.6 \times 10^6 \;J$

$2.33 \times 10^{-3} \; kW\;h$ – x

$x = \frac{(2.33 \times 10^{-3}) \times (3.6 \times 10^6)}{1} = 8399 \;J$

E = 8400 J