PhysicsMagnetismA-Level
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Magnetic force Calculator

Force on a current-carrying conductor in a magnetic field.

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Force

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Overview

The magnetic force formula F=BIL calculates the force exerted on a straight current-carrying conductor when placed inside a uniform magnetic field. This relationship assumes that the current is flowing perpendicular to the magnetic field lines to achieve maximum force.

Symbols

Variables

B = Magnetic Flux Density, I = Current, L = Length of Conductor, F = Force

Magnetic Flux Density
Current
Length of Conductor
Force

Apply it well

When To Use

When to use: Apply this equation when a straight wire is positioned within a constant magnetic field and you need to determine the mechanical force acting on it. It is primarily used when the angle between the current and the magnetic field is 90 degrees.

Why it matters: This principle is the core physical foundation behind the operation of electric motors, which drive everything from industrial machinery to household appliances. Understanding this force allows engineers to design precise control systems for loudspeakers, galvanometers, and magnetic levitation technologies.

Avoid these traps

Common Mistakes

  • Using the charge formula instead of current.
  • Forgetting length is in meters.

One free problem

Practice Problem

A straight wire with a length of 0.5 meters carries a steady current of 4.0 Amperes. If it is placed in a uniform magnetic field of 0.2 Teslas perpendicular to the field lines, calculate the magnitude of the magnetic force acting on the wire.

Magnetic Flux Density0.2 T
Current4 A
Length of Conductor0.5 m

Solve for:

Hint: Multiply the magnetic field strength by the current and the length of the wire segment.

The full worked solution stays in the interactive walkthrough.

References

Sources

  1. Halliday, Resnick, Walker, Fundamentals of Physics
  2. Wikipedia: Magnetic force
  3. Britannica: Magnetic force
  4. NIST CODATA
  5. IUPAC Gold Book
  6. Wikipedia: Tesla (unit)
  7. Wikipedia: Newton (unit)
  8. Halliday, Resnick, Walker, Fundamentals of Physics, 10th Edition