Physics

Physics

Problem

A galvanometer of resistance GG is converted into a voltmeter of range 0−1V0 - 1V by connecting a resistance R1R_1 in series with it. The additional resistance that should be connected in series with R1R_1 to increase the range of the voltmeter to 0−2V0 - 2V will be : a. GG b. R1R_1 c. R1−GR_1 - G d. R1+GR_1 + G
Intuitive explanation

The key insight is that a voltmeter works by limiting current through the galvanometer—a higher voltage range requires a larger series resistance to keep the same full-scale current. When you double the voltage range, you need to double the total resistance in the circuit, so you must add an extra resistor in series with the existing one. Think of it as "spreading out" the voltage drop across more resistance so the galvanometer sees the same safe current at twice the applied voltage.

Intuitive explanation

The key insight is that a voltmeter works by limiting current through the galvanometer—a higher voltage range requires a larger series resistance to keep the same full-scale current. When you double the voltage range, you need to double the total resistance in the circuit, so you must add an extra resistor in series with the existing one. Think of it as "spreading out" the voltage drop across more resistance so the galvanometer sees the same safe current at twice the applied voltage.

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