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Alternating Current question

2024 · 8 Apr · Shift 2 · Q81
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Alternating Current question

2024 · 8 Apr · Shift 2 · Q81

JEE MainPhysicsAlternating CurrentNumerical+4 / −1
An alternating emf E=1102sin⁡100t\mathrm{E}=110 \sqrt{2} \sin 100 \mathrm{t}E=1102​sin100t volt is applied to a capacitor of 2μF2 \mu \mathrm{F}2μF, the rms value of current in the circuit is ‾mA\underline{\hspace{2cm}}\mathrm{mA}​mA.
Numerical answer
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Correct answer: 22

  1. Given alternating emf

    E=1102sin⁡(100t) VE = 110\sqrt{2}\sin(100t)\ \text{V}E=1102​sin(100t) V

    Comparing with the standard form

    E=E0sin⁡(ωt)E = E_0\sin(\omega t)E=E0​sin(ωt)

    we get:

    • Peak voltage: E0=1102 VE_0 = 110\sqrt{2}\ \text{V}E0​=1102​ V
    • Angular frequency: ω=100 rad/s\omega = 100\ \text{rad/s}ω=100 rad/s
  2. Find rms voltage

    For a sinusoidal source,

    Vrms=E02=11022=110 VV_{\text{rms}} = \frac{E_0}{\sqrt{2}} = \frac{110\sqrt{2}}{\sqrt{2}} = 110\ \text{V}Vrms​=2​E0​​=2​1102​​=110 V

  3. Given capacitance

    C=2 μF=2×10−6 FC = 2\,\mu\text{F} = 2\times 10^{-6}\ \text{F}C=2μF=2×10−6 F

  4. Current in a purely capacitive AC circuit

    The rms current is

    Irms=Vrms⋅ωCI_{\text{rms}} = V_{\text{rms}}\cdot \omega CIrms​=Vrms​⋅ωC

    Substituting values:

    Irms=110×100×2×10−6I_{\text{rms}} = 110 \times 100 \times 2\times 10^{-6}Irms​=110×100×2×10−6

    Irms=110×2×10−4I_{\text{rms}} = 110 \times 2\times 10^{-4}Irms​=110×2×10−4

    Irms=2.2×10−2 AI_{\text{rms}} = 2.2\times 10^{-2}\ \text{A}Irms​=2.2×10−2 A

  5. Convert to mA

    2.2×10−2 A=22 mA2.2\times 10^{-2}\ \text{A} = 22\ \text{mA}2.2×10−2 A=22 mA

  6. Final answer

    22\boxed{22}22​

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