Question

To make the magnetic field radial in a moving coil galvanometer:-
A: The number of turns in the coil is increased.
B: Magnet is taken in the form of horse-shoe.
C: Poles are cylindrically out.
D: Coil is wound on an aluminium frame.

Answer 1

This question deals with the constructional area of the moving coil galvanometer. Some features are added on to the device to enhance its characteristic properties. The answer is related to the working of the moving coil galvanometer because only then, we will be able to get a reason behind the presence of the magnetic field radial in it, and the method to implement it. We can approach the question in this manner.

Complete step by step answer:
A moving coil galvanometer helps to measure the value of the electric current with the help of a moving coil that is incorporated in it. Usually, a certain value of a radial magnetic field is applied to the moving coil galvanometer to create a steady torque on the spiral that causes the deflections. This causes a more accurate generation of the values.

To implement the same, the poles of the magnet are cut in a concave shape to make the magnetic field perpendicular to it. This helps in attaining a maximum torque and a radial magnetic field. The concave nature is easily achieved using a cylindrical magnet.
Thus the poles are cylindrically cut to make the magnetic field radial in a moving coil galvanometer.

Hence, option C is correct among the given options.

Note: Moving coil galvanometer is a very delicate device that measures very low values of current, which are in terms of microamperes. The amount of current that passes through the coil is determined by observing the deflection that occurs in the coil. This is caused due to the torque that acts on it. In other words, the amount of current is proportional to the angle of deflection.