Describe the working principle of a moving coil galvanometer. Why is necessary to use
(i) a radial magnetic field and
(ii) a cylindrical soft iron core in a galvanometer ?
Write the expression for current sensitivity of the galvanometer .
Can a galvanometer as such be used for measuring the current ? Explain.

Explanation

### Step-by-Step Solution:

**1. Working Principle of a Moving Coil Galvanometer:**

The working principle of a moving coil galvanometer is based on the interaction between a magnetic field and a current-carrying coil. When a current flows through the coil, it generates a magnetic field around it. If this coil is placed in a uniform magnetic field, it experiences a torque due to the interaction of the magnetic field with the magnetic field produced by the coil. This torque causes the coil to rotate, leading to a deflection of the pointer attached to it.

- **Torque (τ)** experienced by the coil can be expressed as:
\[
...