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Question: Answered & Verified by Expert
A voltmeter of resistance $150 \Omega$ connected across a cell of e.m.f. $3 \mathrm{~V}$ reads $2.5 \mathrm{~V}$. What is the internal resistance of the cell?
PhysicsCurrent ElectricityMHT CETMHT CET 2023 (10 May Shift 1)
Options:
  • A $10 \Omega$
  • B $15 \Omega$
  • C $20 \Omega$
  • D $30 \Omega$
Solution:
2072 Upvotes Verified Answer
The correct answer is: $30 \Omega$
Internal resistance,
$\begin{aligned}
\mathrm{r} & =\left[\frac{\mathrm{E}}{\mathrm{V}}-1\right] \mathrm{R} \\
& =\left[\frac{3}{2.5}-1\right] 150 \\
& =30 \Omega
\end{aligned}$

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