# 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.
• The range of a galvanometer is increased by converting it into an ammeter.

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

# Ammeter-

• An ammeter is a device that is used to measure electric current through a circuit element.
• It is always connected in series with the circuit element through which the current is to be measured.
• To ensure that its insertion in the circuit does not change the current, an ammeter is designed to have very small effective resistance.
• An ideal ammeter has zero resistance.

# Conversion of Galvanometer Into Ammeter-

 To convert a galvanometer into an ammeter, A small resistance of suitable value is connected in parallel with the galvanometer. The resistance connected in this way is called a shunt.

The value of shunt resistance depends on the desired range of the current to be measured.

## Diagram-

The following diagram shows the conversion of a galvanometer into an ammeter-

### Calculating Value of Shunt Resistance-

Let-

• Rg = Resistance of the galvanometer
• Rs = Shunt resistance
• Ig = Full scale deflection current i.e. current required to produce full scale deflection in the galvanometer
• 0-I = Desired current range of the ammeter

As galvanometer and shunt are connected in parallel, so-

Potential difference across the galvanometer = Potential difference across the shunt

Ig x Rg = (I – Ig) x Rs

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

### Important Note

Before converting a galvanometer into an ammeter 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 ammeter is given by-

#### MCQs Quiz-

MCQs Quiz on Conversion of Galvanometer into Ammeter

#### Worksheet-

Worksheet on Conversion of Galvanometer into Ammeter

#### Next Article-

Conversion of Galvanometer into Voltmeter

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