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Topic: Displacement current· Electromagnetic Waves

A capacitor of capacitance 'C', is connected across an ac source of voltage V, given byV = V_0 ω tThe displacement current between the plates of the capacitor, would then be given by :

1. \(I_d = V_0\omega C\cos\omega t\)

2. \(I_d = \dfrac{V_0}{\omega C}\cos\omega t\)

3. \(I_d = \dfrac{V_0}{\omega C}\sin\omega t\)

4. \(I_d = V_0\omega C\sin\omega t\)

1 answer

Best answer

Answer: 1. \(I_d = V_0\omega C\cos\omega t\)

Key idea: displacement current equals the conduction current that charges the capacitor.

\(q = CV = CV_0\sin\omega t\)

\(I_d = I_c = \dfrac{dq}{dt} = CV_0\omega\cos\omega t\)

This matches option 1. Options 2 and 3 divide by \(\omega C\) instead of multiplying (the capacitive reactance is \(X_C=1/\omega C\), so the amplitude is \(V_0/X_C=V_0\omega C\)), and option 4 has \(\sin\) instead of \(\cos\); the current leads the voltage by 90°.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report
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