JEE MainPhysicsCurrent Electricity
A galvanometer can be converted into an ammeter of range 0.5 A by connecting a shunt of 5 . The same galvanometer can be converted into an ammeter of range 2.3 A by connecting a shunt of 1 . The resistance of the galvanometer is
Options
- A45
- B50
- C40
- D55
Correct answer
A. 45
Step-by-step solution
Let I_g be the full-scale deflection current and G be the resistance of the galvanometer. For the first conversion (range I₁ = 0.5 A , shunt S₁ = 5 ): I_g G = (I₁ - I_g) S₁ I_g (G + 5) = 0.5 5 I_g (G + 5) = 2.5 (1) For the second conversion (range I₂ = 2.3 A , shunt S₂ = 1 ): I_g G = (I₂ - I_g) S₂ I_g (G + 1) = 2.3 1 I_g (G + 1) = 2.3 (2) Dividing equation (1) by equation (2) to eliminate I_g : G + 5 G + 1 = 2.5 2.3 Cross-multiplying: 2.3 (G + 5) = 2.5 (G + 1) 2.3 G + 11.5 = 2.5 G + 2.5 Rearranging to solve for G :