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Alternating Current question

2025 · 4 Apr · Shift 2 · Q72
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Alternating Current question

2025 · 4 Apr · Shift 2 · Q72

JEE MainPhysicsAlternating CurrentNumerical+4 / −1
An inductor of self inductance 1 H is connected in series with a resistor of 100π100 \pi100π ohm and an ac supply of 100π100 \pi100π volt, 50 Hz . Maximum current flowing in the circuit is ‾\underline{\hspace{2cm}}​ A.
Numerical answer
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Correct answer: 1

  1. Given data
  • Inductance: L=1 HL = 1\,\text{H}L=1H
  • Resistance: R=100π ΩR = 100\pi\,\OmegaR=100πΩ
  • AC voltage: V=100π VV = 100\pi\,\text{V}V=100πV
  • Frequency: f=50 Hzf = 50\,\text{Hz}f=50Hz

We interpret the given AC supply voltage as rms voltage, which is standard unless otherwise stated.

  1. Find angular frequency
ω=2πf=2π(50)=100π rad/s\omega = 2\pi f = 2\pi(50) = 100\pi\,\text{rad/s}ω=2πf=2π(50)=100πrad/s
  1. Find inductive reactance
XL=ωL=(100π)(1)=100π ΩX_L = \omega L = (100\pi)(1) = 100\pi\,\OmegaXL​=ωL=(100π)(1)=100πΩ
  1. Find impedance of series RRR-LLL circuit
Z=R2+XL2Z = \sqrt{R^2 + X_L^2}Z=R2+XL2​​

Since R=100πR = 100\piR=100π and XL=100πX_L = 100\piXL​=100π,

Z=(100π)2+(100π)2Z = \sqrt{(100\pi)^2 + (100\pi)^2}Z=(100π)2+(100π)2​ Z=100π2 ΩZ = 100\pi\sqrt{2}\,\OmegaZ=100π2​Ω
  1. Find rms current
Irms=VrmsZ=100π100π2=12 AI_{\text{rms}} = \frac{V_{\text{rms}}}{Z} = \frac{100\pi}{100\pi\sqrt{2}} = \frac{1}{\sqrt{2}}\,\text{A}Irms​=ZVrms​​=100π2​100π​=2​1​A
  1. Find maximum current

For sinusoidal current,

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

So,

I0=2(12)=1 AI_0 = \sqrt{2}\left(\frac{1}{\sqrt{2}}\right) = 1\,\text{A}I0​=2​(2​1​)=1A
  1. Final answer
1\boxed{1}1​

The maximum current flowing in the circuit is 1 A1\,\text{A}1A.

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