Current Electricity

JEE Main level, single correct, medium

239 of 380

Question 239 of 380

Two identical heater filaments are connected first in parallel and then in series. At the same applied voltage, the ratio of heat produced in same time for parallel to series will be:

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Answer: (B) 4:14:1

Let the resistance of the filaments be RR and the voltage be VV.
For the series combination the power is
P1=(V22R){P}_{1}=\left(\dfrac{{V}^{2}}{2R}\right)
For parallel combination,
P2=V2(R2)=(2V2R){P}_{2}=\dfrac{{V}^{2}}{\left(\dfrac{R}{2}\right)}=\left(\dfrac{2{V}^{2}}{R}\right)
Hence, the ratio is
⇒P2P1=41\Rightarrow \dfrac{{P}_{2}}{{P}_{1}}=\dfrac{4}{1}

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