With reference to free electron theory of conductivity, explain the terms :
(1) Drift speed (2) Relaxation time

Explanation

To explain the terms "drift speed" and "relaxation time" in the context of the free electron theory of conductivity, we can break down the concepts as follows:

### Step-by-Step Solution:

1. **Drift Speed**:
- **Definition**: Drift speed refers to the average velocity that free electrons attain due to an applied electric field in a conductor.
- **Explanation**: In metals, free electrons move randomly at high velocities. However, when an electric field is applied, these electrons experience a force that causes them to drift in a specific direction, albeit at a much lower average speed compared to their random motion.
- **Collisions**: As these electrons move, they frequently collide with positive ions (the fixed lattice structure of the metal). Each collision alters their direction of motion, which means that while they have a net drift in the direction of the electric field, their individual paths are still random.
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