a. Calculate the inductance of an air core solenoid containing `300` turns if the length of the solenoid is `25.0cm` and its cross -sectional area is `4.00cm^2`.
b. Calculate the self -induced emf in the solenoid if the current through it is decreasingg at the rate of `50.0A//s`.

Explanation

To solve the problem, we will break it down into two parts as given in the question.

### Part a: Calculate the inductance of the air core solenoid.

1. **Given Data:**
- Number of turns (N) = 300
- Length of the solenoid (L) = 25.0 cm = 0.25 m
- Cross-sectional area (A) = 4.00 cm² = 4.00 × 10⁻⁴ m²
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