The main purpose of use of shunt in ammeter is to bypass the current. The ammeter can carry a small amount of current though it. Therefore, to measure a large current a shunt diverts the current in two parts. The larger part of the current flows through the shunt resistance & small current as per the ammeter rating flows through the ammeter. In this article, we will take some numerical problems to understand the use of shunt in ammeter.
A 20 ohm shunt is joined with an ammeter with 200 ohm resistance. It is joined to a 10v battery having a resistance of 4 ohm. What will the observation of the ammeter be?
The circuit diagram of the problem is as given below. Ammeter shunt value is as shown in the circuit. The ammeter shunt is used to divert most of the circuit current towards shunt resistance and fraction of current towards the ammeter.
Total resistance of the circuit(R)
= 4+(200 x 20/220)
= 4+ 18.18
Total current of the circuit
I = V/R= 10/22.18=0.45 Amps
The current through ampere meter
= 0.45 x 20/220b =0.0409 Amps.
= 40.9 mA