Question

(a) What is the meaning of electric power of an electrical device? Write its SI unit.

(b) An electric kettle of $2kW$ is used for $2h$. Calculate the energy consumed in
(i) kilowatt hour and
(ii) joules.

Answer 1

a) Electric power of an electrical device is defined as its rate of consumption of electrical energy.
i.e., $P=\frac{E}{t}$
The $SI$ unit of electrical power is watt $\left(W\right)$

(b) $P=2kW,t=2h$
(i) $E=P\times t=2\times 2=4kWh$
(ii) $E=2000W\times 2\times 3600s$
$=1.44\times {10}^{7}J$