What is the effect of metallic core on self inductance?

Explanation

To understand the effect of a metallic core on self-inductance, we can break down the concepts involved step by step.

### Step 1: Understanding Self-Inductance
Self-inductance (L) is a property of a coil (or inductor) that quantifies its ability to induce an electromotive force (emf) in itself due to a change in current. The formula for self-inductance is given by:

\[ L = \frac{N^2 \mu A}{l} \]

where:
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