Question

A certain household has consumed $250units$ of energy during a month. How much energy is this in joules?

Answer 1

Step 1: Definition of $1-Kilowatthour\left(kWh\right)$

1. $1kWh$ is the energy consumed by an appliance of power $1kW$ when used for $1$hour.
2. It is a commercial unit of electricity.

Step 2: Calculation of energy in $Joules\left(J\right)$

$$\begin{gathered} 1kWh=1kW\times 1h \\ =1000W\times 60\times 60s \\ =3.6\times {10}^{6}J \end{gathered}$$

Therefore, the energy, $E$ is given by:

$$\begin{gathered} E=250units \\ =250kWh \\ =250\times 3.6\times {10}^{6}J \\ =900\times {10}^{6}J \\ =9\times {10}^{8}J \end{gathered}$$

Hence, the household has consumed $9\times {10}^{8}J$ of energy during the month.