# Moving Coil Galvanometer-

Before you go through this article, make sure that you have gone through the previous article on Moving Coil Galvanometer.

We have learnt-

• A galvanometer is an instrument that is used to detect small currents in an electric circuit.
• An ordinary galvanometer gives a full scale deflection with a small current of few μA.

In this article, we will learn the conversion of a galvanometer into a voltmeter.

# Voltmeter-

• A voltmeter is a device used to measure potential difference across any two points in an electric circuit.
• It is always connected in parallel with the circuit element across which the potential difference is to be measured.
• A voltmeter is designed to have very high effective resistance.
• An ideal voltmeter has infinite resistance.

# Conversion of Galvanometer Into Voltmeter-

 To convert a galvanometer into a voltmeter, A high resistance of suitable value is connected in series with the galvanometer.

The value of high resistance depends on the desired range of the voltmeter.

## Diagram-

The following diagram shows the conversion of a galvanometer into a voltmeter-

### Calculating Value of High Resistance-

Let-

• Rg = Resistance of the galvanometer
• R = High resistance to be connected in series
• Ig = Full scale deflection current i.e. current required to produce full scale deflection in the galvanometer
• 0-V = Desired range of the voltmeter

Using Ohm’s law, we must have-

V = Ig x (Rg + R)

From here, the value of high resistance is given by-

### Important Note

Before converting a galvanometer into a voltmeter of desired range, we must know-

• Resistance of the galvanometer (Rg)
• Full scale deflection current of the galvanometer (Ig)

### Effective Resistance-

The effective resistance of the converted voltmeter is given by-

#### MCQs Quiz-

MCQs Quiz on Conversion of Galvanometer into Voltmeter

#### Worksheet-

Worksheet on Conversion of Galvanometer into Voltmeter

Get more notes & other study material of the Chapter Moving Charges & Magnetism.