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JEE Main 2002 (AIEEE) · Electrical Power & Heating Effect

Electrical Power & Heating Effect question from JEE Main 2002 (AIEEE)

Q87JEE Main 2002 · AIEEEEasy

Electrical Power & Heating Effect

A wire when connected to $220\text{ V}$ mains supply has power dissipation $P_1.$ Now the wire is cut into two equal pieces which are connected in parallel to the same supply. Power dissipation in this case is $P_2.$ Then $P_2 : P_1$ is

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Answer: (b)

Each half has resistance $\frac{R}{2}$ ; two in parallel give $\frac{R}{4}$ .
At fixed $V$ , $P = \frac{V^2}{R} \propto \frac{1}{R}$ .
$\frac{P_2}{P_1} = \frac{R}{R/4} = 4$ .
So the answer is (b) 4.

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