Question

An electric heater is rated $4\mathrm{kW},220\mathrm{V}.$ Find the cost of using this heater for $12$ hours if one $\mathrm{kWh}$ of the electrical energy costs$₹3.25$.

Answer 1

Step 1: Given data

$$\begin{gathered} \mathrm{Power}=4\mathrm{kW} \\ \mathrm{Voltage}=220\mathrm{V} \\ \mathrm{Time}=12\mathrm{hours} \end{gathered}$$

Cost of electrical heater$=Rs3.25$

Step 2: Finding the cost of the heater

Number of units$=\frac{\text{Power}\times \text{Time}}{1000}$

$$\begin{gathered} =\frac{4000\times 12}{1000} \\ =48 \end{gathered}$$

Cost of the electrical heater of $1$ kWh$=3.25$

Cost of the electrical heater of $48$ units$=48\times 3.25$

$=\mathrm{Rs}156$

Hence, the number of units of electrical heaters is $48$ and the cost of a heater is $Rs156$.