Moving Charges and Magnetism · NEET Preparation Physics

A galvanometer of resistance G is converted into a voltmeter to measure up to V volts by connecting a resistance R1 in series. If it is to be convert…

Practice question from Moving Charges and Magnetism (NEET Preparation Physics), with the correct answer and a step-by-step solution.

medium · MCQ · Q-173A54

A galvanometer of resistance $G$ is converted into a voltmeter to measure up to $V$ volts by connecting a resistance $R_1$ in series. If it is to be converted to measure up to $2V$ volts, the series resistance required is $R_2$ . The relation between $R_1$ and $R_2$ is:

A. $R_2 = 2R_1 + G$ Correct answer
B. $R_2 = 2R_1 - G$
C. $R_2 = R_1 + G$
D. $R_2 = 2R_1$

Solution

For a voltmeter, $V = I_g(G + R_1) \implies R_1 = \frac{V}{I_g} - G$ . For voltage $2V$ , $2V = I_g(G + R_2) \implies R_2 = \frac{2V}{I_g} - G$ . Substituting $V/I_g = R_1 + G$ , we get $R_2 = 2(R_1 + G) - G = 2R_1 + G$ .

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