Question

Which of the following characteristics of electrons determines the current in a conductor?

Options

• Drift velocity alone

• Thermal velocity alone

• Both drift velocity and thermal velocity

• Neither drift nor thermal velocity

Answer 1

Drift velocity alone

Explanation:

Drift velocity is the average uniform velocity acquired by free electrons inside a metal by the application of an electric field, which is responsible for the current through it

The direction of drift velocity for electrons in a metal is opposite to that of applied electric field (i.e. current density `vec J`).

V_d ∞ E, i.e., the greater the electric field, the larger will be the drift velocity.

The relationship between current and drift speed is given by I = ne Av_d

Here, l is the current, and v_d is the drift velocity.

So, I ∞ v_d

Thus, only drift velocity determines the current in a conductor.

Remember the direction of drift velocity and current is opposite, so we are taking the magnitude of drift velocity or drift speed of free electrons.