Physics Current Electricity PMDC 2021
PMDC Verified Question 76 of 112
A load of resistance 0.04 \(\Omega\) is attached to the cell having E.M.F 1.5 V and 15 A is drawn in the circuit. The internal resistance of cell will be
A
0.6 \(\Omega\)
B
0.06 \(\Omega\)
C
6 \(\Omega\)
D
0.3 \(\Omega\)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: 0.06 \(\Omega\)
Concept:

The total resistance of a circuit includes both external load resistance and the internal resistance of the battery.

Formula:

$$ I = \frac{E}{R + r} $$

Solution:

  • Given \( I = 15 \text{ A} \), \( E = 1.5 \text{ V} \), \( R = 0.04 \, \Omega \).


  • Rearrange for total resistance: \( R + r = \frac{E}{I} \).


  • \( 0.04 + r = \frac{1.5}{15} = 0.1 \, \Omega \).


  • \( r = 0.1 - 0.04 = 0.06 \, \Omega \).


Why other options are incorrect:

  • Opt A: Decimal error (0.1 - 0.04 is not 0.6).


  • Opt C: Drastic decimal misplacement.

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