In moving coil galvanometer, strong horse shoe magnet of concave shaped pole pieces is used to (a) increase space for rotation of coil (b) reduce weight of galvanometer (c) produce magnetic field which is parallel to plane of coil at any position (d) make magnetic induction weak at the centre.

Answer: (c). Concave pole pieces with a soft-iron core make the field radial. In a radial field the plane of the coil stays parallel to B in every position, so torque = NIAB for all deflections. This gives I ∝ θ and a linear scale. So the answer is (c).

In moving coil galvanometer, strong horse shoe magnet of concave… | MHT CET 2019 (2 May, Shift 1)

Q154MHT CET 2019 · 2 MAY · SHIFT 1Easy

Kirchhoff's Laws & Measuring Instruments

In moving coil galvanometer, strong horse shoe magnet of concave shaped pole pieces is used to

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Answer: (c)

Concave pole pieces with a soft-iron core make the field radial.
In a radial field the plane of the coil stays parallel to $\vec B$ in every position, so torque $= NIAB$ for all deflections.
This gives $I \propto \theta$ and a linear scale.
So the answer is (c).

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