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
Ig – Current through the galvanometer
Rs – Resistance of the shunt
Rg – 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.
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: