Define current density. Write an expression which connects current density with drift speed.

Explanation

**Step-by-Step Solution:**

1. **Definition of Current Density:**
Current density (denoted as \( J \)) is defined as the amount of electric current flowing through a unit cross-sectional area of a conductor. It quantifies how much current is passing through a specific area and is given by the formula:
\[ J = \frac{I}{A} \]
where:
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