4.28 A galvanometer coil has a resistance of 15 and the metre shows full scale deflection for a current of 4 mA. How will you convert the metre into an ammeter of range 0 to 6 A?

Resistance of the galvanometer coil, G = 15 Ω
Current for which the galvanometer shows full scale deflection,
Ig=4mA=4×10-3A
Range of the ammeter is 0, which needs to be converted to 6 A.
Current,I=6A
A shunt resistor of resistance S is to be connected in parallel with the galvanometer to convert it into an ammeter. The value of S is given as:
S=IgGI-Ig
=4×10-3×156-4×10-3
S=6×10-26-0.004=0.065.996
0.01Ω=10
Hence, a shunt resistor is to be connected in parallel with the galvanometer.