Magnetic Force on a Wire Calculator
Calculate the Lorentz force on a straight current-carrying wire in a uniform magnetic field.
About magnetic force on a current-carrying wire
Wire-force examples
These examples use a straight wire in a uniform field.
| Inputs | Results | Interpretation |
|---|---|---|
| I = 5 A, L = 2 m, B = 0.3 T, θ = 90° | F = 3 N, B⊥ = 0.3 T | The 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 T | Only half the field is perpendicular. |
| I = 10 A, L = 0.25 m, B = 0.8 T, θ = 0° | F = 0 N, B⊥ = 0 T | Parallel current and field produce no force. |
How to calculate force
- Enter the conventional current magnitude in amperes.
- Enter only the wire length located within the magnetic field.
- Provide magnetic flux density in teslas and the angle between current and field.
- 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.