How can a moving coil galvanometer be converted into a voltmeter?

The correct answer is Option (2) → By connecting a high resistance in series

A voltmeter is joined in parallel with the section whose voltage it measures. It must draw only a very small current, or it will disturb the circuit. For this, its total resistance must be very large.

Option (1) By connecting a low resistance in series — Incorrect. A low resistance in series hardly raises the total resistance. So the meter would still draw a large current from the section it is measuring.

Option (2) By connecting a high resistance in series — Correct. A large resistance \( R \) in series makes the total resistance \( R_G+R\approx R \) very large. So the instrument draws a tiny current, and its scale is calibrated to read the voltage.

Option (3) By connecting a high resistance in parallel — Incorrect. A resistance in parallel with the galvanometer can only lower the total resistance below \( R_G \), never make it large.

Option (4) By connecting a low resistance in parallel — Incorrect. A small shunt resistance in parallel converts the galvanometer into an ammeter, which has a very low resistance.

NCERT (2026-27):
The Moving Coil Galvanometer – “The galvanometer can also be used as a voltmeter to measure the voltage across a given section of the circuit. For this it must be connected in parallel with that section of the circuit. Further, it must draw a very small current, otherwise the voltage measurement will disturb the original set up by an amount which is very large. … To ensure this, a large resistance R is connected in series with the galvanometer.”