Shunts and Multipliers

1. Shunt:

A shunt is a low resistance usually used to convert a galvanometer to an ammeter. It is usually connected in parallel with the galvanometer.


I – Current to be measured

I– Current through the galvanometer

R– Resistance of the shunt

R– Resistance of galvanometer

Note: The voltage across the shunt is the same as that across galvanometer.



A galvanometer gives a full scale deflection when a current of 10mA flows through it. How would  you convert it to an ammeter capable of reading 3Aif the resistance of the galvanometer is 5Ω?


To do this, we connect a resistor of low resistance called shunt in parallel with the galvanometer.  The value of such shunt is calculated below:



p.d across galvanometer = p.d across shunt


Thus, a shunt of 0.0167Ω is needed.

2. Multiplier:

A multiplier is a high resistance usually used to convert a galvanometer to a voltmeter. It is usually connected in series with the galvanometer.


To convert a galvanometer to a voltmeter ,we need a multiplier Rso that the galvanometer could  read 20V at full scale deflection of 10mA. Find the value of R if the internal resistance of the  galvanometer is 6Ω. Solution:



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