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-

• R_g = Resistance of the galvanometer
• R_s = Shunt resistance
• I_g = 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

I_g x R_g = (I – I_g) x R_s

 

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.