Question

Charge velocity is defined as the:
1. holes moving at the Fermi speed
2. electrons moving at the Fermi speed
3. speed with which the effect of EMF is experienced at all parts of the conductor resulting in the flow of current
4. speed with which charge drifts in a conductor

Answer 1

Correct Answer - Option 4 : speed with which charge drifts in a conductor

Explanation:

When electric field is applied to a material then the charges inside the material attains a velocity and starts to move in a direction depending upon the direction of applied electric field. The velocity attained by charge particle is known as charge velocity or drift velocity.

The drift velocity of an electron is defined as

V_d = μE 

Here, μ = Mobility of the electron,

E = Applied electric field.

V_d = Drift velocity

∴ Charge velocity is defined as the speed with which charge drifts in a conductor.

Formula of drift velocity in terms of current density,

I = nA V_d Q

\(\frac{I}{A} = n V_d Q\), where \(\frac{I}{A}= I\)

→ I is the current density measured in Amperes per square meter

→ n is the number of electrons

→ Q is the charge of an electron which is measured in columns

→ unit of drift velocity is metre/second.

→ Mobility is quantity, which is used to find how mobile a particular charge particle is its unit is m²/(v - s) or cm²/(v - e).

→ The mobility of electron is normally 2.5 times than that of mobility of holes.