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