Define the term self indutance of a solenoid. Obtained the expresssion for the magnetic energy stored in an inductor or self-inductance L to a build up a certain I through it.

Explanation

### Step-by-Step Solution

**Step 1: Define Self-Inductance of a Solenoid**
Self-inductance (L) is a property of a coil (like a solenoid) that quantifies its ability to induce an electromotive force (emf) in itself when the current flowing through it changes. When the current increases, the magnetic flux through the coil also increases, which according to Faraday's law of electromagnetic induction, induces an emf in the coil itself. This phenomenon is known as self-induction.

**Step 2: Formula for Self-Inductance**
The self-inductance of a solenoid can be expressed mathematically as:
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