The galvanometer cannot as such be used as an
ammeter to measure the value of the current in a given circuit This is for
two reasons: (i) Galvanometer is a very sensitive device, it gives a full-
scale deflection for a current of the order of mA (ii) For measuring currents,
the galvanometer has to be connected in series, and as it has a large
resistance, this will change the value of the current in the circuit To
overcome these difficulties, one attaches a small resistance rs, called shunt
resistance, in parallel with the galvanometer coil; so that most of the
current passes through the shunt