Physics Current Electricity MDCAT 2017
PMDC Verified Question 97 of 112
When the current is neither drawn from a source nor given to it then:
A
\( E = V_t \)
B
\( E > V_t \)
C
\( V_t > E \)
D
Both "B" & "C"
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: \( E = V_t \)
Concept:

The relationship between electromotive force (E) and terminal voltage (\(V_t\)) depends on whether the circuit is open or closed.

Formula:

$$ V_t = E - Ir $$

Solution:

  • When no current is drawn or given, the circuit is open, meaning \( I = 0 \).


  • Substitute \( I = 0 \) into the terminal voltage equation: \( V_t = E - (0)r \).


  • Therefore, \( V_t = E \). The terminal voltage exactly equals the EMF.


Why other options are incorrect:

  • Opt B: This occurs when the cell is discharging (supplying current).


  • Opt C: This occurs when the cell is being charged by an external source.

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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