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NEET 2003 (AIPMT) · Electrical Power & Heating Effect

Electrical Power & Heating Effect question from NEET 2003 (AIPMT)

Q84NEET 2003 · AIPMTMedium

Electrical Power & Heating Effect

An electric kettle has two heating coils. When one of the coils is connected to an a.c. source, the water in the kettle boils in 10 minutes. When the other coil is used the water boils in 40 minutes. If both the coils are connected in parallel, the time taken by the same quantity of water to boil will be

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Answer: (a)

Same heat $H$ , so $P \propto 1/t$ .
Parallel powers add: $\dfrac{1}{t} = \dfrac{1}{10} + \dfrac{1}{40} = \dfrac{5}{40}$ .
$t = 8\text{ min}$ , so the answer is (a) 8 minutes.

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