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Question: Answered & Verified by Expert
Two cells having unknown e.m.f.s $\mathrm{E}_{1}$ and $\mathrm{E}_{2}\left(\mathrm{E}_{1}>\mathrm{E}_{2}\right)$ are connected in potentiometer circuit so as to assist each other. The null point obtained is at 490
$\mathrm{cm}$ from the higher potential end. When cell $\mathrm{E}_{2}$ is connected so as to oppose cell $\mathrm{E}_{1}$,
Ithe null point is obtained at $90 \mathrm{~cm}$ from the same end. The ratio of the e.m.f.s of
two cells $\left(\frac{\mathrm{E}_{1}}{\mathrm{E}_{2}}\right)$ is
PhysicsCurrent ElectricityMHT CETMHT CET 2020 (19 Oct Shift 2)
Options:
  • A $0.689$
  • B $0 \cdot 182$
  • C $5 \cdot 33$
  • D $1 \cdot 45$
Solution:
2892 Upvotes Verified Answer
The correct answer is: $1 \cdot 45$
(A)
$\begin{aligned} \frac{E_{1}}{E_{2}} &=\frac{\ell_{1}+\ell_{2}}{\ell_{1}-\ell_{2}} \\ &=\frac{490+90}{490-90}=\frac{580}{400}=1.45 \end{aligned}$

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