A metre bridge experiment, the resistance in the left gap is $20 \Omega$ and in the right gap is $60 \Omega$. The bridge is balanced. The distance of the null point from the centre of the wire 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: Use resistance per length:
Total resistance $80\ \Omega$ is shared along 100 cm. Left $20\ \Omega$ takes $\dfrac{20}{80}$ of the length.

Step 2: Length:
$\dfrac{20}{80}\times100 = 25$ cm from the left.

Step 3: Offset from the centre:
$|50 - 25| = 25$ cm, option (C).

Final Answer:
The null point is 25 cm from the centre. \[ \boxed{\text{(C) }25\ \text{cm}} \]

A metre bridge experiment, the resistance in the left gap is \(20 \Omega\) and in the right gap is \(60 \Omega\). The bridge is balanced. The distance of the null point from the centre of the wire is

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The Correct Option is C

Solution and Explanation

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