Carrier transport — definition of mobility In metals (and more generally in conductors/semiconductors), the average electron drift velocity per unit electric field is called mobility. True or false?

Introduction / Context:
Mobility quantifies how quickly charge carriers move through a material under an applied electric field. It is central to understanding conductivity, device speed, and scattering mechanisms in metals and semiconductors.

Given Data / Assumptions:

• Drift regime with a uniform electric field E.
• Average drift velocity v_d well defined.
• Ohmic behavior holds within the considered field range.

Concept / Approach:
Mobility μ is defined by μ = v_d / E. Electrical conductivity is then σ = q n μ for a single carrier type (electrons), or σ = q (n μ_n + p μ_p) in semiconductors with both carriers. Thus, the statement precisely matches the definition.

Step-by-Step Solution:
Let E be the applied field.Electrons attain average drift velocity v_d opposite to E.Define mobility μ so that v_d = μ E (magnitude).Hence, “drift velocity per unit field” is exactly mobility.

Verification / Alternative check:
Dimensional check: [μ] = (m/s)/(V/m) = m^2/(V·s), agreeing with standard units.

Why Other Options Are Wrong:
“False” would contradict the accepted definition used in basic solid-state physics and electronics.

Common Pitfalls:
Confusing mobility with diffusivity; though related by the Einstein relation, they are distinct quantities.

Final Answer:
True