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Question: Answered & Verified by Expert
A potentiometer wire of length $100 \mathrm{~cm}$ and resistance $3 \Omega$ is connected in series
with resistance of $8 \Omega$ and an accumulator of 4 volt whose internal resistance is
$1 \Omega$
A cell of e.m.f. 'E' is balanced by $50 \mathrm{~cm}$ length of the wire. The e.m.f. of the
cell is
PhysicsCurrent ElectricityMHT CETMHT CET 2020 (19 Oct Shift 1)
Options:
  • A $1 \cdot 00$ volt.
  • B $0 \cdot 75$ volt.
  • C $0 \cdot 50$ volt.
  • D $0 \cdot 25$ volt.
Solution:
1217 Upvotes Verified Answer
The correct answer is: $0 \cdot 50$ volt.
(C)
Total resistance $=3+8+1=12 \Omega$ current. $\quad I=\frac{E}{R}=\frac{4}{12}=\frac{1}{3} A$
P.D. across the wire $=I R_{\omega}=\frac{1}{3} \times 3=1 \mathrm{~V}$
potential gradient $\mathrm{K}=\frac{\mathrm{V}}{\mathrm{L}}=\frac{1}{1}=1 \mathrm{v} / \mathrm{m}$ $\mathrm{E}^{\prime}=\mathrm{K} \ell^{\prime}=1 \times 0.5=0.5 \mathrm{~V}$

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