Physics

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Drift Velocity Calculator.

Calculate charge-carrier drift speed from current, carrier density, charge, and area.

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Drift velocity: 0.000073 m/s

Drift velocity

0.000000m/s

Results update automatically as you type.

Use Cases

Physics Education

Helps students and educators understand the relationship between current, carrier density, and drift velocity in conductors.

Example: Calculate the drift velocity of electrons in a copper wire with a given current and cross-sectional area.

Electrical Engineering Design

Assists engineers in estimating carrier speeds in conductive materials to evaluate performance and safety.

Example: Determine if drift velocity in a power cable is within expected limits for a given load.

Frequently Asked Questions

What is drift velocity?
Drift velocity is the average speed at which charge carriers, such as electrons, move through a conductor when an electric field is applied. It is typically very slow, on the order of millimeters per second, despite the fast propagation of the electric field.
How is drift velocity calculated?
Drift velocity (v) is calculated using the formula v = I / (n * q * A), where I is the current in amperes, n is the carrier number density in m⁻³, q is the charge magnitude in coulombs, and A is the conductor's cross-sectional area in m².
What units are used in this calculator?
The calculator uses SI units: current in amperes (A), carrier number density in m⁻³, charge magnitude in coulombs (C), and conductor area in square meters (m²). The resulting drift velocity is in meters per second (m/s).

Tips & Common Mistakes

Tips

  • Ensure carrier number density is in m⁻³; for copper, it's approximately 8.5 × 10²⁸ m⁻³.
  • Use consistent units: convert area to m² if given in mm² or cm².
  • Remember that drift velocity is an average; individual electrons move randomly at much higher speeds.
  • For semiconductors, carrier density can vary with doping; use the appropriate value for your material.

Common Mistakes to Avoid

  • Forgetting to convert area from mm² to m² (1 mm² = 1 × 10⁻⁶ m²).
  • Using the charge of an electron (1.6 × 10⁻¹⁹ C) but not accounting for the sign; this calculator uses magnitude.
  • Confusing carrier number density with mass density; they are different properties.

Last updated: August 13, 2026