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Current Electricity question

2022 · 28 Jul · Shift 2 · Q62
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Current Electricity question

2022 · 28 Jul · Shift 2 · Q62

JEE MainPhysicsCurrent ElectricityNumerical+4 / −1
An electrical bulb rated 220 V, 100 W, is connected in series with another bulb rated 220 V, 60 W. If the voltage across combination is 220 V, the power consumed by the 100 W bulb will be about ‾\underline{\hspace{2cm}}​ W.
Numerical answer
View written solutionFree

Correct answer: 14

  1. Find the resistance of each bulb from its rating

For a bulb rated at voltage VVV and power PPP, R=V2PR=\frac{V^2}{P}R=PV2​

So,

  • For the 100 W100\,\text{W}100W bulb: R1=2202100=484 ΩR_1=\frac{220^2}{100}=484\,\OmegaR1​=1002202​=484Ω

  • For the 60 W60\,\text{W}60W bulb: R2=220260=4840060≈806.67 ΩR_2=\frac{220^2}{60}=\frac{48400}{60}\approx 806.67\,\OmegaR2​=602202​=6048400​≈806.67Ω

  1. Since the bulbs are in series, total resistance is Req=R1+R2=484+806.67=1290.67 ΩR_{\text{eq}}=R_1+R_2=484+806.67=1290.67\,\OmegaReq​=R1​+R2​=484+806.67=1290.67Ω

  2. Find the current through the series combination

Same current flows through both bulbs: I=VReq=2201290.67≈0.1705 AI=\frac{V}{R_{\text{eq}}}=\frac{220}{1290.67}\approx 0.1705\,\text{A}I=Req​V​=1290.67220​≈0.1705A

  1. Power consumed by the 100 W bulb

Using P=I2RP=I^2RP=I2R, P1=I2R1=(0.1705)2×484P_1=I^2R_1=(0.1705)^2\times 484P1​=I2R1​=(0.1705)2×484 P1≈0.0291×484≈14.1 WP_1\approx 0.0291\times 484\approx 14.1\,\text{W}P1​≈0.0291×484≈14.1W

So the power consumed by the 100 W100\,\text{W}100W bulb is about 14 W\boxed{14\,\text{W}}14W​

  1. Comparison with stored answer

Stored correct answer = 141414

Our derived answer = 141414

Hence, they agree.

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