An air cored solenoid is of length 0.3 m, area of cross section `1.2 xx 10^(-3) m^(2)` and has 2500 turns. Around its central section, a coil of 350 turns is wound. The solenoid and the coil are electrically insulated from eachother. Calculate the e.m.f. induced in the coil if the initial current of 3 A in the solenoid is reversed in 0.25 s.

Explanation

To solve the problem step by step, we will calculate the induced electromotive force (e.m.f.) in the coil wound around the solenoid when the current in the solenoid is reversed.

### Step 1: Identify the given values
- Length of the solenoid, \( L = 0.3 \, \text{m} \)
- Area of cross-section, \( A = 1.2 \times 10^{-3} \, \text{m}^2 \)
- Number of turns in the solenoid, \( N_1 = 2500 \)
- Number of turns in the coil, \( N_2 = 350 \)
- Initial current, \( I_1 = 3 \, \text{A} \)
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