A coil develops heat of $800\, cal/sec$. When $20\, volts$ is applied across its ends. The resistance of the coil is .............. $\Omega$ ($1$ $cal$ = $4.2$ $joule$)
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(c) $H = \frac{{{V^2}t}}{{4.2\,R}}$ or $\frac{H}{t} = \frac{{{V^2}}}{{4.2\,R}}$
$ \Rightarrow $ $800 = \frac{{20 \times 20}}{{4.2 \times R}}$$ \Rightarrow $$R = \frac{5}{{42}} = 0.119 \approx 0.12\,\Omega $
$ \Rightarrow $ $800 = \frac{{20 \times 20}}{{4.2 \times R}}$$ \Rightarrow $$R = \frac{5}{{42}} = 0.119 \approx 0.12\,\Omega $
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