Question

Under an external electric field electrons drift slowly inside the conductor.

1. The velocity of drift is

• 1 mm/s
• 10⁵ m/s
• 3 × 10⁸ m/s
• 3 × 10⁹ m/s

2. What is meant by relaxation time?

3. Write an expression for drift velocity in terms of relaxation time.

4. When temperature increases what happens to drift velocity?

Answer 1

1. 1 mm/s.

2. The average time between two successive collision is called relaxation time.

3.  V_d = \(\frac{eE}{m}t\)

4. We know drift velocity

V_d = \(\frac{eE}{m}t\)

When temperature increases, relaxation time decreases. As a result drift velocity decreases.