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Alternating Current question

2025 · 3 Apr · Shift 2 · Q69
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Alternating Current question

2025 · 3 Apr · Shift 2 · Q69

JEE MainPhysicsAlternating CurrentMCQ+4 / −1
An electric bulb rated as 100 W−220 V100 \mathrm{~W}-220 \mathrm{~V}100 W−220 V is connected to an ac source of rms voltage 220 V. The peak value of current through the bulb is :
  1. A
    0.32 A
  2. B
    0.64 A
  3. C
    0.45 A
  4. D
    2.2 A
View written solutionFree

Correct answer: B

  1. Use the bulb rating to find the rms current

For a bulb rated 100 W−220 V100\,\text{W}-220\,\text{V}100W−220V, when connected to 220 V220\,\text{V}220V rms supply:

P=VrmsIrmsP = V_{\text{rms}} I_{\text{rms}}P=Vrms​Irms​

So,

Irms=PVrms=100220=0.4545 AI_{\text{rms}} = \frac{P}{V_{\text{rms}}} = \frac{100}{220} = 0.4545\,\text{A}Irms​=Vrms​P​=220100​=0.4545A

  1. Relate peak current and rms current

For alternating current,

I0=2 IrmsI_0 = \sqrt{2}\, I_{\text{rms}}I0​=2​Irms​

Thus,

I0=2×0.4545≈1.414×0.4545≈0.643 AI_0 = \sqrt{2} \times 0.4545 \approx 1.414 \times 0.4545 \approx 0.643\,\text{A}I0​=2​×0.4545≈1.414×0.4545≈0.643A

  1. Match with the options

I0≈0.64 AI_0 \approx 0.64\,\text{A}I0​≈0.64A

So the correct option is B.

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