A current 4.0 A exist in a wire of cross-sectional area `2.0 mm^(2)`. If each cubic metre of the wire contains `12.0xx10^(28)` free electrons, then the drift spped is

Explanation

To find the drift speed of electrons in a wire carrying a current, we can use the relationship between current (I), charge density (n), charge of an electron (e), and drift speed (v_d). Here’s a step-by-step solution:

### Step 1: Identify the given values
- Current (I) = 4.0 A
- Cross-sectional area (A) = 2.0 mm² = 2.0 × 10⁻⁶ m² (since 1 mm² = 10⁻⁶ m²)
- Number of free electrons per cubic meter (n) = 12.0 × 10²⁸ m⁻³
- Charge of an electron (e) = 1.6 × 10⁻¹⁹ C

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