Physics Current Electricity ETEA 2019
PMDC Verified Question 88 of 112
A car battery has EMF of 12 Volts and internal resistance \(5 \times 10^{-2} \text{ ohm}\). If it draws 60 ampere current, then terminal voltage of the battery will be
A
5 volts
B
3 volts
C
15 volts
D
9 volts
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: 9 volts
Concept:

When a battery outputs heavy current (like starting a car), there is a significant voltage drop across its internal resistance.

Formula:

$$ V_t = E - Ir $$

Solution:

  • EMF \( E = 12 \text{ V} \).


  • Internal resistance \( r = 0.05 \, \Omega \).


  • Current \( I = 60 \text{ A} \).


  • Voltage drop \( Ir = 60 \times 0.05 = 3 \text{ V} \).


  • Terminal voltage \( V_t = 12 - 3 = 9 \text{ V} \).


Why other options are incorrect:

  • Opt B: This is the internal voltage drop (\(Ir\)), not the terminal voltage.


  • Opt C: This would be the voltage if the battery were being charged (\(12 + 3 = 15\text{V}\)).

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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