(a) Calculate the self-inductance of a solenoid that is tightly wound with wire of diameter `0.10 cm`, has a cross-sectional area `0.90 cm^2` and is `40 cm` long
(b) If the current through the solenoid decreases uniformly from `10` A to `0 A` in `0.10 s`, what is the emf induced between the ends of the solenoid?

Explanation

### Step-by-Step Solution

#### Part (a): Calculate the self-inductance of the solenoid.

1. **Identify Given Values**:
- Diameter of wire, \( d = 0.10 \, \text{cm} = 0.0010 \, \text{m} \)
- Cross-sectional area, \( A = 0.90 \, \text{cm}^2 = 0.90 \times 10^{-4} \, \text{m}^2 \)
- Length of the solenoid, \( L = 40 \, \text{cm} = 0.40 \, \text{m} \)
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