COMEDK202510 May 2025Evening ShiftPhysicsMagnetic Effects of CurrentActual
The wire made of Phosphor bronze is used as the suspension strip in the moving coil galvanometer, because:
Options
- AIts restoring torque per unit twist is very large
- BIt has less tensile strength
- CIt is more flexible
- DIts restoring torque per unit twist is small.
Correct answer
D. Its restoring torque per unit twist is small.
Step-by-step solution
The moving coil galvanometer operates on the principle of balancing the magnetic deflecting torque with the restoring torque of the suspension strip. The deflecting torque is given by _ d = NIAB , where N is the number of turns, I is the current, A is the area, and B is the magnetic field. The restoring torque is given by _ r = k , where k is the restoring torque per unit twist of the suspension strip. For a sensitive galvanometer, a small current I should produce a large deflection . Since = NIAB k , a small value