Correct Answer - Option 4 : Flux density in the air gap becomes high thereby a large deflecting torque is produced
D’Arsonval Galvanometer: Used to measure small voltage and current in the circuit.
It is a center zero value measuring instrument.
Advantages of placing iron core between the permanent magnet pole faces:
- Provides the uniform air gap between the coil sides and pole faces.
- Reduces the gap between coil sides and pole faces of the coil. Therefore it increases the magnetic linkage with the coil.
- The sensitivity of the D’Arsonval galvanometer increases.
- The deflection torque of the coil is directly proportional to the current through it. Therefore we can obtain a uniform scale of the instrument.