Question

An electric iron is rated $220\mathrm{V},1KW$. Under normal working conditions, find the power consumed if the line voltage falls to $180\mathrm{V}$

Answer 1

Step 1: Given data:

The voltage of electric iron $=220V$

Power of electric iron $=1KW$

Here, we have to determine the power consumed when the line voltage is $180\mathrm{V}$

Step 2: Calculating the resistance of iron:
The formula for finding the power when voltage and resistance is given is:
$P=\frac{V^2}{R}$,
Where, $PisthePower,VistheVoltage,RistheResis\tan ce$

So, for determining the value of resistance we will put the given value in above expression,

Thus the value of the resistance will be

$$\begin{gathered} R=\frac{V^2}{P} \\ =\frac{220\times 220}{1000} \\ =48.4\Omega \end{gathered}$$

Step 3: Calculation of power when the line voltage is $180\mathrm{V}$

As we know,
The formula for finding the power $P=\frac{V^2}{R}$

So, the value of the power will be $P=\frac{{180}^2}{48.4}=\frac{180\times 180}{48.4}=669.42Watt$

Hence, the value of the power when the line voltage is $180\mathrm{V}$ will be $669.42Watt$