Current Electricity

JEE Main level, single correct, medium

256 of 380

Question 256 of 380

Two equal resistances when connected in series to a battery, consume electric power of 60 W60 \mathrm{~W}. If these resistance are now connected in parallel combination to the same battery, the electric power consumed will be :

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Answer: (B) 240 W240 \mathrm{~W}

When two resistances are connected in series, Req=2RR_{e q}=2 R

Power consumed, P=ε2Rea=ε22R\mathrm{P}=\frac{\varepsilon^{2}}{\mathrm{R}_{\mathrm{ea}}}=\frac{\varepsilon^{2}}{2 \mathrm{R}}

In parallel condition, Req=R/2\mathrm{R}_{\mathrm{eq}}=\mathrm{R} / 2 New power, P′=ε2(R/2)\mathrm{P}^{\prime}=\frac{\varepsilon^{2}}{(\mathrm{R} / 2)}

or P′=4P=240 W(∵P=60 W)\mathrm{P}^{\prime}=4 \mathrm{P}=240 \mathrm{~W}(\because \mathrm{P}=60 \mathrm{~W})

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