NEET-XII-Physics
33: Thermal and Chemical Effects of Electric Current
- #3The 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?Ans : 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\,\mathrm{\,\Omega \,}``
Now, P = 1000 W
`` \Rightarrow R=\frac{{V}^{2}}{P}=\frac{{\left(250\right)}^{2}}{1000}=62.5\,\mathrm{\,\Omega \,}``
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