Lorentz force calculator

Type B [T], I [A] and l [m]. The calculator computes F = B I l at 90°: 0.5 T, 2 A and 0.1 m is 0.1 N, and 1.5 T, 8 A and 0.2 m is 2.4 N. Zero amperes gives zero newtons.

Current: I = Q/t. Faraday induction: EMF = ΔΦ/Δt.

Inputs

Result

Induction B (T), Current I (A) and Length l in the field (m). The result shows up here.

How it works

F I → B ⊗ F = B · I · l 90°
A current-carrying wire in field B, angle 90°: F = B·I·l.

Force on a straight wire in a B field at 90° is F = B I l. At 0.5 T, 2 A and 0.1 m you get 0.1 N. At 1.5 T, 8 A and 0.2 m you get 2.4 N. At 0.8 T, 0.5 A and 0.02 m you get 0.008 N. At 0.2 T, 10 A and 0.25 m you get 0.5 N.

The form has three fields: B in teslas, I in amperes, l in meters. The result is in newtons. The angle is always 90°, the maximum. Another angle would need sin θ, which this calculator does not have. A comma and a period are the same B: 0,5 and 0.5.

B, I, and l must be positive. Typed 0 in any field gives F = 0: no field, no current, or no length in the field. All three fields need a number before 0.1 N can appear.

I = Q/t is on the neighbouring page: that I goes into the formula. Faraday is EMF from ΔΦ/Δt, volts, not newtons. F = m a is another path to the same unit N. Coulomb force is F = k q₁ q₂ / r², not B I l.

The calculator does not draw a right-hand rule. It computes the F magnitude at 90°. Direction stays with the problem.

Type 0.5, 2, and 0.1, click Calculate, and match 0.1 N. The header symbol does not pull the wire. Treat 0.1 N as the value at perpendicular B and I, not as a rail model.

How to use

  1. In the first field enter B in teslas, for example 0.5.
  2. In the second enter I in amperes, for example 2. In the third, l in meters, for example 0.1.
  3. Click Calculate. The calculator multiplies B I l at 90°. 0.5, 2, and 0.1 give 0.1 N.
  4. B, I, and l must be positive. Typed 0 gives F = 0. All three fields need a number.
  5. For I = Q/t, open current. Faraday is on EMF = ΔΦ/Δt. Here it stays F = B I l.

Formula

F = B · I · l

Angle 90°. B > 0, I > 0, l > 0. Unit of F: newton.

F, B, I, and l in the Lorentz force

Force on a straight wire at 90°: F = B·I·l. 0.5 T, 2 A and 0.1 m is 0.1 N. 1.5 T, 8 A and 0.2 m is 2.4 N.

F
Force [N]. 0.5 × 2 × 0.1 = 0.1 N. Not Coulomb k q1 q2 / r².
B
Magnetic induction [T]. 0.5 T or 1.5 T. Must be positive.
I
Current in the wire [A]. 2 A. The model angle is 90°.
l
Length of the segment in the field [m]. 0.1 m. Not the torque arm r.

Real-life examples

Example 1

B = 0.5 T, I = 2 A, l = 0.1 m -> F = 0.10 N.

Example 2

B = 0.8 T, I = 0.5 A, l = 0.02 m -> F = 0.008 N.

Example 3

B = 0.2 T, I = 10 A, l = 0.25 m -> F = 0.50 N.

Example 4

B = 5e-5 T, I = 1 A, l = 1 m -> F = 0.00 N.

Example 5

B = 1.2 T, I = 3 A, l = 0.15 m -> F = 0.54 N.

Example 6

B = 0.4 T, I = 4 A, l = 0.05 m -> F = 0.08 N.

Example 7

B = 0.5 T, I = 2 A, l = 0.4 m -> F = 0.40 N.

Example 8

B = 1.5 T, I = 8 A, l = 0.2 m -> F = 2.40 N.

Ways to use this calculator

  • You compute 0.1 N from 0.5 T, 2 A, and 0.1 m.
  • You compare 0.1 N with 2.4 N at 1.5 T, 8 A, and 0.2 m.

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Frequently asked questions

How much F at 0.5 T, 2 A and 0.1 m?

Force is 0.1 N. That is the product 0.5 × 2 × 0.1. The angle in this model is 90°, a full product with no sinφ.

Which units do I type?

Field B [T], current I [A], length l [m]. Result F [N]. Type a centimetre as 0.01, not as 1.

What if I = 0?

Force is 0 N. No current means no Lorentz force on the wire. The other two fields still need a number.

Can the angle be other than 90°?

The calculator uses φ = 90°. At another angle sinφ enters and F drops. There is no angle field here.

How is this different from F = m·a?

Here force from a magnetic field, a current and a segment. There Newton’s second law, mass and acceleration. Different fields, same F [N].

How is this different from Faraday EMF?

Here a force on a current in field B. There a voltage from dB/dt or from motion. Another formula, another calculator.

Does a comma in 0.5 T work?

Yes. 0.5 and 0,5 mean the same B [T]. F = B I l uses that field.

Where is I = Q/t?

On the current-from-charge page. That I later enters F = B I l. Here current is an input, not a result.

How much at 0.2 T, 10 A and 0.25 m?

Force is 0.5 N. 0.2 × 10 × 0.25, with the wire perpendicular to B.

How much at 0.8 T, 0.5 A and 0.02 m?

You get 0.008 N. A weak current, a short segment, a small force.

Knowledge sources

The formula is the school one. Units follow SI; NIST SP 330 and BIPM define the measures, not your result.

Page updated in 2026.