Physics Alternating Current PMDC Conceptual Practice
PMDC Verified Question 58 of 127
An AC ammeter connected in series with a pure capacitor reads \(5\text{ A}\) when supplied by a \(220\text{ V}\) AC line. What is the average power consumed by the capacitor?
A
1100 W
B
0 W
C
550 W
D
220 W
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: 0 W
Concept:

In a purely capacitive circuit, the current and voltage are \(90^\circ\) out of phase, so the power factor is \(\cos(90^\circ) = 0\).

Formula / Reaction:

$$P_{\text{avg}} = V_{\text{rms}} I_{\text{rms}} \cos\phi = (220\text{ V})(5\text{ A})\cos(90^\circ) = 0\text{ W}$$

Solution:

  • Although current flows, it is purely reactive current that transfers zero net average power.


Why other options are incorrect:

  • Opt_A: \(1100\text{ W}\) is the apparent power \(V_{\text{rms}} I_{\text{rms}}\).


  • Opt_C: Half of apparent power.


  • Opt_D: Incorrect value.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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