Question

An electrical heater of resistance 10 Ω draws a steady current of 5 A from the service mains for 2 hours. Find the power of this heater and the amount of energy consumed by the heater in kilowatt-hour.

Answer 1

Power and energy calculation:

Given: \(R = 10 \, \Omega\), \(I = 5 \, \text{A}\), \(t = 2 \, \text{hours} = 7200 \, \text{s}\)

First, we calculate the power (\(P\)) of the heater using the formula:

\[ P = I^2 R = (5 \, \text{A})^2 \times 10 \, \Omega = 250 \, \text{W} = 0.25 \, \text{kW} \]

Next, we find the energy (\(E\)) consumed by the heater using:

\[ E = P t = 0.25 \, \text{kW} \times 2 \, \text{h} = 0.5 \, \text{kWh} \]

Therefore, the power of the heater is \(250 \, \text{W}\) (or \(0.25 \, \text{kW}\)), and the energy consumed is \(0.5 \, \text{kWh}\).