Magnetic Force on a Wire Calculator

Calculate the Lorentz force on a straight current-carrying wire in a uniform magnetic field.

Current-carrying wire force
Enter current, active wire length, field strength, and their angle.

About magnetic force on a current-carrying wire

A conductor carrying electric current experiences a force when it lies in a magnetic field. At the microscopic level, moving charge carriers experience the Lorentz force. The forces transferred through the conductor combine into the macroscopic wire relation F = BIL sin(θ), where B is magnetic flux density, I is current, L is the wire length inside the field, and θ is the angle between conventional current direction and the magnetic field. The result is measured in newtons when SI units are used. Only the magnetic field component perpendicular to current contributes. This component is B sin(θ), which the calculator reports along with force. A wire perpendicular to the field at 90 degrees experiences maximum force. A wire parallel or antiparallel to the field at 0 or 180 degrees has zero magnetic force because the cross product vanishes. Angles with the same sine produce the same force magnitude, though vector direction still depends on the actual orientation. Use Fleming's left-hand rule or the vector product L × B to determine force direction. Point the current-length vector with conventional current and combine it with magnetic field direction; the force is perpendicular to both. Reversing either current or field reverses force. Reversing both leaves force direction unchanged. This calculator reports magnitude rather than a three-dimensional vector, so direction must be established from the physical arrangement. The equation assumes a straight segment, uniform field, steady current, and a wire thin enough that the same field applies across it. If field strength changes along the conductor, calculate the vector force by integrating I dL × B over the path. Curved wires can also require segment-by-segment vector addition. The active length is only the portion actually inside the magnetic field, not necessarily the conductor's total length. Enter amperes, metres, teslas, and degrees exactly as labelled. This relation supports motor-force estimates, electromagnetic actuator analysis, loudspeaker examples, laboratory demonstrations, and introductory physics problems. Real equipment may also need thermal, mechanical, fringe-field, and support-force analysis. The output provides a reliable ideal value and exposes the perpendicular field component so you can see directly how orientation reduces force from its maximum BIL value.

Wire-force examples

These examples use a straight wire in a uniform field.

InputsResultsInterpretation
I = 5 A, L = 2 m, B = 0.3 T, θ = 90°F = 3 N, B⊥ = 0.3 TThe perpendicular orientation gives maximum force.
I = 4 A, L = 0.5 m, B = 0.2 T, θ = 30°F = 0.2 N, B⊥ = 0.1 TOnly half the field is perpendicular.
I = 10 A, L = 0.25 m, B = 0.8 T, θ = 0°F = 0 N, B⊥ = 0 TParallel current and field produce no force.

How to calculate force

  1. Enter the conventional current magnitude in amperes.
  2. Enter only the wire length located within the magnetic field.
  3. Provide magnetic flux density in teslas and the angle between current and field.
  4. Select Calculate wire force to find the force and perpendicular field component.

Frequently asked questions

Why does the formula include sine?

Magnetic force comes from a vector cross product, so only the field component perpendicular to current contributes. Sine converts the full field magnitude into that perpendicular component.

When is force on the wire maximum?

Force is maximum when current and magnetic field are perpendicular at 90 degrees. In that orientation sin(θ) equals one and the magnitude simplifies to BIL.

How do I find the force direction?

Use Fleming's left-hand rule or the vector direction of L × B. Reversing current or field reverses force, while this calculator reports only its magnitude.

Which wire length should I enter?

Enter the straight conductor length actually exposed to the stated magnetic field. Do not include wire outside the field region because it does not contribute under this model.

Does this work for a nonuniform field?

The displayed equation assumes one uniform field over the whole active segment. For a changing field or curved wire, integrate the vector force along the conductor instead.