28. A galvanometer coil has a resistance of 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?
The galvanometer can be converted into an ammeter by connecting an appropriate resistor of resistance R in series with it.
At the full-scale deflection current(I) of 4 mA, the ammeter must measure a current of 6 A.
The resistance of the galvanometer coil is G =
Since the resistor and galvanometer coil are connected in parallel the potential difference is the same across them.
The galvanometer can be converted into an ammeter by connecting a resistor of resistance in parallel with it.