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Alternating Current
AC Voltage Applied to a Capacitor
4 questions from 4 papers, each with its answer.
- questions
- 4
- papers
- 4
- years asked, 2017–2026
- 2 of 10
- of Alternating Current
- 6.67%
Appears in
Concepts tested
- Capacitive reactance 2
- AC voltage applied to a capacitor
- rms current through a capacitor
All Questions
2022 Phase 2 1 question
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Given below are two statements. Statement I: In an ac circuit, the current through a capacitor leads the voltage across it. Statement II: In a.c circuits containing pure capacitance only, the phase difference between the current and the voltage is $\pi$. In the light of the above statements, choose the most appropriate answer from the options given belowIn a purely capacitive AC circuit the current leads the voltage by a phase of $\frac{\pi}{2}$, not $\pi$. So Statement I is correct and Statement II is incorrect.
2020 1 question
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A $40\ \mu F$ capacitor is connected to a 200 V, 50 Hz ac supply. The rms value of the current in the circuit is, nearly:$i_{rms} = \frac{\varepsilon_{rms}}{X_C} = \varepsilon_{rms}\,\omega C$, with $\omega = 2\pi f = 100\pi$ $i_{rms} = 200 \times 2\pi \times 50 \times 40 \times 10^{-6}$ $= 2.5$ A
2011 AIPMT-PRE 1 question
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In an ac circuit an alternating voltage $e = 200\sqrt{2}\sin100t$ volts is connected to a capacitor of capacity 1 $\mu$F. The r.m.s. value of the current in the circuit isComparing with $e = e_0\sin\omega t$: $e_0 = 200\sqrt{2}$ V and $\omega = 100$ rad/s.
$e_{rms} = \frac{e_0}{\sqrt{2}} = \frac{200\sqrt{2}}{\sqrt{2}} = 200$ V
Capacitive reactance $X_C = \frac{1}{\omega C} = \frac{1}{100\times1\times10^{-6}} = 10^4\ \Omega$
$I_{rms} = \frac{e_{rms}}{X_C} = \frac{200}{10^4} = 2\times10^{-2}$ A
$I_{rms}$ = 20 mA
2001 AIPMT 1 question
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A capacitor of capacity C has reactance X. If capacitance and frequency become double then reactance will be : -Capacitive reactance: $X_C = \dfrac{1}{2\pi fC}$, so $X_C \propto \dfrac{1}{fC}$.
When both f and C are doubled: $X' = \dfrac{1}{2\pi(2f)(2C)} = \dfrac{1}{4} \times \dfrac{1}{2\pi fC}$
$X' = \dfrac{X}{4}$