What is drift velocity? Establish a relation between current and drift velocity?

Explanation

### Step-by-Step Solution

1. **Definition of Drift Velocity**:
Drift velocity (vd) is defined as the average velocity of charge carriers (typically electrons) in a conducting wire when an electric field is applied. It represents the net velocity of the charge carriers in the direction of the electric field.

2. **Understanding Charge Density**:
Let’s denote:
- \( n \) = number of charge carriers per unit volume (number density)
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