A long solenoid of radius 2 cm has 100 turns/cm and carries a current of 5A. A coil of radius 1 cm having 100 turns and a total resistance of 20 Omega is placed inside the solenoid coaxially. The coil is connected to a galvanometer. If the current in the solenoid is reversed in direction, find the charge flown through the galvanometer.

Explanation

To solve the problem, we need to find the charge that flows through the galvanometer when the current in the solenoid is reversed. We will follow these steps:

### 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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