JEE Main202624 January 2026Evening ShiftPhysicsCurrent ElectricityActual
A moving coil galvanometer of resistance 100 shows a full scale deflection for a current of 1 mA. The value of resistance required to convert this galvanometer into an ammeter, showing full scale deflection for a current of 5 mA, is _ _ _ _
Options
- A0.5
- B2.5
- C10
- D25
Correct answer
D. 25
Step-by-step solution
To convert a galvanometer to an ammeter, a shunt resistance S is connected in parallel. For full-scale deflection: Current through galvanometer: I_g = 1 mA Total current: I = 5 mA Current through shunt: I_s = 5 - 1 = 4 mA Since voltage across both is equal: I_g G = I_s S 0.001 100 = 0.004 S S = 0.1 0.004 = 25 Ω