JEE Main · PhysicsHard
In a potentiometer circuit, a cell of emf $E$ is balanced by a length $l$. If the internal resistance of the cell is $r$ and it is shunted by a resistance $R$, the new balancing length is $l'$. What is the ratio $l'/l$?
- A.$\frac{R}{R + r}$
- B.$\frac{r}{R + r}$
- C.$\frac{R}{r}$
- D.$\frac{R + r}{R}$
Show correct answer & step-by-step solution
Correct answer: A — $\frac{R}{R + r}$
Solution
The potentiometer measures the terminal voltage . With shunt , . Since , the ratio .
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