Enter the current flow, free electron density, charge, and cross-sectional area into the calculator to determine the drift velocity.

Drift Velocity Formula

The formula for calculating drift velocity is as follows: 

u = I / (n*A*q)
  • Where u is the drift velocity (m/s)
  • I is the current (amps)
  • A is the cross-sectional area (m^2)
  • n is the free electron density (e/m^3)
  • q is the charge (C)

To calculate the drift velocity, divide the current by the product of the cross-sectional area, free electron density, and charge.

Drift Velocity Definition

Adrift velocity is defined as the average speed of charged particles in a material due to an electric field acting on them.

Is drift velocity constant?

Adrift velocity is constant as long as the cross-sectional area and electric field stay constant along the full length of the wire or material.

Is drift velocity independent of area?

No, drift velocity is directly dependent on the cross-sectional area of the wire or material. This can be seen in the formula for drift velocity, u = I / (n*A*q), where A is the cross-sectional area.

Is drift velocity independent of diameter?

Drift velocity does depend on diameter, because as the formula shows, the drift is dependent on the cross-sectional area, and the cross-sectional area is determined by the diameter of the wire.

On what factors does drift velocity depend on?

The factors that influence drift velocity are; current, electron density, cross-sectional area, and electron charge. Any factors that go into these values should also be considered.

How does drift velocity depend on electric field?

The drift velocity is directly proportional to drift velocity. This can be seen in the alternative formula to the one shown above, u = v*E, where v is the electron mobility, and E is the electric field.

Why is drift velocity negative?

Drift velocity should come out negative in your calculation because the charge of an electron is always negative, therefore, the solution to the formula above will yield a negative velocity. To fix this, use the magnitude of the charge of one electron instead.

How to calculate drift velocity?

  1. First, determine the current along the wire or material.
  2. Next, determine the free electron density. This is the density per unit volume.
  3. Next, determine the cross-sectional area of the wire.
  4. Next, determine the electron charge (1.6*10^-19 C)
  5. Finally, calculate the drift velocity using the formula or calculator above.
drift velocity calculator
drift velocity formula