Physics Alternating Current BUMHS 2025
PMDC Verified Question 74 of 127
If the capacitance in a purely capacitive AC circuit is doubled, the current will be:
A
Double
B
Become half
C
Remain same
D
Decrease to the fourth
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Double
Concept:

In an AC circuit containing a pure capacitor, alternating current is inversely proportional to capacitive reactance and directly proportional to capacitance.

Formula / Reaction:

$$I = \frac{V}{X_C} = 2\pi f C V$$

Solution:

  • Capacitive reactance is defined as \(X_C = \frac{1}{2\pi f C}\).


  • Substituting \(X_C\) into the current equation gives \(I = \frac{V}{X_C} = 2\pi f C V\).


  • Because current is directly proportional to capacitance (\(I \propto C\)), doubling the capacitance (\(C' = 2C\)) results in doubling the current (\(I' = 2I\)).


Why other options are incorrect:

Because current increases in direct proportion to capacitance (\(I \propto C\)), it cannot be halved, remain unchanged, or decrease to one-fourth.

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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