In an experiment to find emf of a cell using potentiometer, the length of null point for a cell of emf $1.5$ V is found to be $60$ cm. If this cell is replaced by another cell of emf $E$, the length of null point increases by $40$ cm. The value of $E$ is $x/10$ V.
The value of $x$ is

Question

A galvanometer has resistance $ G = 100 \, \Omega $ and shows full-scale deflection at $ I_q = 1 \, \text{mA} $. To convert it into a voltmeter of range 5 V, what resistance should be connected in series?

Answer 1

Step 1: Plan:
Find the potential gradient first.

Step 2: Steps:
Gradient $= \frac{1.5}{60} = 0.025$ V/cm. For the new cell, the balancing length is $100$ cm, so $E = 0.025\times100 = 2.5$ V $= \frac{25}{10}$ V, which gives $x = 25$.

Final Answer:
The value of $x$ is $25$, option (B). \[ \boxed{25} \]

In an experiment to find emf of a cell using potentiometer, the length of null point for a cell of emf \(1.5\) V is found to be \(60\) cm. If this cell is replaced by another cell of emf \(E\), the length of null point increases by \(40\) cm. The value of \(E\) is \(x/10\) V.
The value of \(x\) is

Show Hint

The Correct Option is B

Solution and Explanation

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In an experiment to find emf of a cell using potentiometer, the length of null point for a cell of emf \(1.5\) V is found to be \(60\) cm. If this cell is replaced by another cell of emf \(E\), the length of null point increases by \(40\) cm. The value of \(E\) is \(x/10\) V.The value of \(x\) is