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Alternating Current question

2025 · 4 Apr · Shift 1 · Q56
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Alternating Current question

2025 · 4 Apr · Shift 1 · Q56

JEE MainPhysicsAlternating CurrentMCQ+4 / −1
An alternating current is represented by the equation, i=1002sin⁡(100πt)i=100 \sqrt{2} \sin (100 \pi t)i=1002​sin(100πt) ampere. The RMS value of current and the frequency of the given alternating current are
  1. A
    1002 A,100 Hz\frac{100}{\sqrt{2}} \mathrm{~A}, 100 \mathrm{~Hz}2​100​ A,100 Hz
  2. B
    502 A,50 Hz50 \sqrt{2} \mathrm{~A}, 50 \mathrm{~Hz}502​ A,50 Hz
  3. C
    1002 A,100 Hz100 \sqrt{2} \mathrm{~A}, 100 \mathrm{~Hz}1002​ A,100 Hz
  4. D
    100 A,50 Hz100 \mathrm{~A}, 50 \mathrm{~Hz}100 A,50 Hz
View written solutionFree

Correct answer: D

  1. Compare with the standard AC current form

    The given current is i=1002sin⁡(100πt)  Ai = 100\sqrt{2}\sin(100\pi t)\;\text{A}i=1002​sin(100πt)A

    Standard form of alternating current is i=I0sin⁡(ωt)i = I_0 \sin(\omega t)i=I0​sin(ωt)

    So, by comparison: I0=1002  A,ω=100π  rad/sI_0 = 100\sqrt{2}\;\text{A}, \qquad \omega = 100\pi\;\text{rad/s}I0​=1002​A,ω=100πrad/s

  2. Find the RMS current

    RMS current is given by Irms=I02I_{\text{rms}} = \frac{I_0}{\sqrt{2}}Irms​=2​I0​​

    Substituting I0=1002I_0 = 100\sqrt{2}I0​=1002​: Irms=10022=100  AI_{\text{rms}} = \frac{100\sqrt{2}}{\sqrt{2}} = 100\;\text{A}Irms​=2​1002​​=100A

  3. Find the frequency

    We know ω=2πf\omega = 2\pi fω=2πf

    Hence, f=ω2π=100π2π=50  Hzf = \frac{\omega}{2\pi} = \frac{100\pi}{2\pi} = 50\;\text{Hz}f=2πω​=2π100π​=50Hz

  4. Match with the options

    We obtained: Irms=100  A,f=50  HzI_{\text{rms}} = 100\;\text{A}, \qquad f = 50\;\text{Hz}Irms​=100A,f=50Hz

    This matches Option D.

  5. Verification with stored answer

    Stored correct answer: D

    Derived answer: D

    So, the derived answer agrees with the stored answer.

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