Question

Define power. What is the SI unit of power? An electric bulb consumes 7.2 kJ of electrical energy in 2 minutes. What is the power of the electric bulb? [5 MARKS]

Answer 1

Definition: 1 Mark
Unit: 1 Mark
Problem: 3 Mark

1. Power is work done per unit time.
2. SI unit of power is Watt
3. We know that:

$Power=\frac{Energyconsumed}{Timetaken}$

Here, Energy consumed = 7.2 kJ

$=7.2\times 1000J$

$=7200J$

Time taken = 2 minutes

$=2\times 60seconds$

$120s$

Now, putting these values of 'energy consumed' and 'time taken' in the above formula, we get:

$Power=\frac{7200J}{120s}$

$=60J/s$

$=60W$

Thus, the power of this electric bulb is 60 watts.