1. Ammeter
2.
A galvanometer can be converted into an ammeter by a low resistance (shunt) connected parallel to it.
Theory:
Let G be the resistance of the galvanometer, giving full deflection fora current Ig . To convert it into an ammeter, a suitable shunt resistance ‘S’ is connected in parallel. In this arrangement, Ig current flows through Galvanometer and remaining (I-Ig) current flows through shunt resistance.
Since G and S are parallel
P.d Across G = p.d across S
Ig x G =(I-Ig)S
S = \(\frac{I_g\,G}{(I-I_g)}\)
Connecting this shunt resistance across galvanometer we can convert a galvanometer into ammeter.
3. Ammeter is a low resistance device. Hence it draws high current. This high current will damage it.