Through a long solenoid of diameter `4.1` cm, having 100 turns per cm, a current I = 1A is flowing. At its centre, a 60 turns closely packed coil of diameter `3.1` cm si placed such that the coil is coaxial with the long solenoid. The current in the solenoid is reduced to zero at a steady rate in 10 ms. What is the magnitude of emf induced in the coil while the current in the solenoid is changing?

Explanation

To solve the problem, we need to determine the induced electromotive force (emf) in the coil placed inside the solenoid as the current in the solenoid decreases to zero. Here’s a step-by-step solution:

### Step 1: Calculate the magnetic field inside the solenoid
The magnetic field \( B \) inside a long solenoid is given by the formula:
\[ B = \mu_0 n I \]
where:
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