Question

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

Answer 1

Step 1- Given data:

Power $P=4kW.$

Voltage difference $V=220V.$

Rate per unit $r=₹3.25perkW-h.$

time $t=12h.$

Step 2- To find out the energy consumed:

The formula for the energy $H=P\times t$

$$\begin{gathered} \Rightarrow H=P\times t \\ \Rightarrow H=4kW\times 12h=48kW-h. \end{gathered}$$

Thus, the energy consumed in $12hours$is $48kW-h.$

Step 3- To find out the cost of electrical energy consumed-

The formula for the cost will be $=r\times H$

$$\begin{gathered} \Rightarrow \cos t=r\times H \\ \Rightarrow \cos t=₹3.25\times 48 \\ \Rightarrow \cos t=₹156 \end{gathered}$$

Thus, the cost of electrical energy used by the heater is $₹156$