Question

The specification on a heater coil is 250 V, 500 W. Calculate the resistance of the coil. What will be the resistance of a coil of 1000 W to operate at the same voltage?

Answer 1

Let R be the resistance of the coil.

The power P consumed by a coil of resistance R when connected across a supply V is given by

\[P = \frac{V^2}{R}\]

\[ \Rightarrow R = \frac{V^2}{P}\]

\[ \Rightarrow R = \frac{\left( 250 \right)^2}{500} = 125 \Omega\]

Now, P = 1000 W

\[\Rightarrow R = \frac{V^2}{P} = \frac{\left( 250 \right)^2}{1000} = 62 . 5 \Omega\]