An ammeter is an instrument which is used to measure current in a circuit in ampere (or milli-ampere or micro ampere). Hence, it is always connected in series in the circuit. Since, the galvanometer coil has some resistance of its own, therefore, to convert a galvanometer into an ammeter, its resistance is to be decreased so, to convert a galvanometer into ammeter a low resistance, called shunt ( *) is connected in parallel to the galvanometer as shown in figure.
where RA = resistance of ammeter
G = resistance of galvanometer
