Question

The motion of an electron inside a conductor is

• A. uniform
• B. accelerated
• C. drifted
• D. retarded

Hint:

Visualize a person trying to walk through a dense, jostling crowd. They are constantly bumped and change direction (collisions), but by persistently pushing in one direction (electric field), they make slow, overall progress. This slow, net progress is the "drift". The electron's path is a chaotic series of short, curved paths, but with a net displacement over time.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
This question asks to describe the overall motion of a free electron inside a conductor when an electric field is applied (i.e., when a current is flowing).
Step 2: Detailed Explanation:
Free electrons in a conductor are in a state of continuous, random motion due to thermal energy, with very high speeds (thermal velocity). They frequently collide with the fixed positive ions of the metallic lattice.
When an external electric field is applied, the electrons experience an electrostatic force in the direction opposite to the field. This force accelerates the electrons. However, this acceleration lasts only for a very short time before the electron collides with a lattice ion. During the collision, the electron loses most of the energy gained from the field and its direction of motion is randomized. It then starts to accelerate again.
This process of acceleration followed by collision repeats continuously. While the instantaneous motion is a series of short accelerations, the *net effect* over a longer period is a slow, average movement in the direction opposite to the electric field. This net motion is called drift. The average velocity of this motion is called the drift velocity (\(v_d\)), which is typically very small (\(\sim 10^{-4}\) m/s) and is constant for a constant electric field.
- Uniform motion is incorrect because the instantaneous velocity is constantly changing.
- Accelerated motion is only partially correct; it describes the motion between collisions but not the overall effect.
- Retarded/Damped motion describes the effect of collisions but not the driving force from the field.
- Drifted motion is the best term to describe the overall, effective motion of the electron that gives rise to electric current.
Step 3: Final Answer:
The net or average motion of an electron inside a conductor under the influence of an electric field is a drift. Therefore, option (C) is the most accurate description.