Physics Alternating Current PMDC Conceptual Practice
PMDC Verified Question 25 of 127
When the frequency of an alternating current source across a pure ohmic resistor is doubled, the electrical resistance of the resistor will:
A
Remain unchanged
B
Be doubled
C
Be halved
D
Become zero
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Remain unchanged
Concept:

Ohmic resistance \(R = \rho \frac{L}{A}\) is an intrinsic property of the material's resistivity and geometric dimensions, completely independent of AC frequency.

Formula / Reaction:

$$R = \frac{V_{\text{rms}}}{I_{\text{rms}}} = \text{constant with respect to } f$$

Solution:

  • Unlike reactive components (inductors and capacitors), an ideal resistor has zero reactance.


  • Changing the AC frequency from \(f\) to \(2f\) does not alter the resistance \(R\).


Why other options are incorrect:

  • Opt_B: Inductive reactance \(X_L\) doubles with frequency, but resistance does not.


  • Opt_C: Capacitive reactance \(X_C\) halves with frequency, but resistance does not.


  • Opt_D: Resistance remains constant and non-zero.

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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