A galvanometer having a coil resistance of 50 is shunted by a resistance of 2 to convert it into an ammeter. If the maximum current this ammeter can measure is 5.2 A , the current required for full-scale deflection of the original galvanometer is

Step-by-step solution

Let I_g be the current required for full-scale deflection of the galvanometer, G be the galvanometer resistance, S be the shunt resistance, and I be the maximum current to be measured. The potential difference across the galvanometer and the shunt must be equal: I_g G = (I - I_g) S Rearranging the terms to solve for I_g : I_g (G + S) = I S I_g = I S G + S Substituting the given values ( G = 50 , S = 2 , I = 5.2 A ): I_g = 5.2 2 50 + 2 I_g = 10.4 52 I_g = 0.2 A Converting to milliamperes: I_g = 0.2 1000 mA = 200 mA