Motor effect Calculator
Direction and magnitude of force on a conductor.
Formula first
Overview
The motor effect describes the physical force exerted on a current-carrying conductor when it is placed within an external magnetic field. This force arises from the interaction between the magnetic field generated by the moving charges in the wire and the surrounding external magnetic field.
Symbols
Variables
B = Magnetic Flux Density, I = Current, L = Length, F = Force
Apply it well
When To Use
When to use: Apply this equation when calculating the magnetic force on a straight conductor of length L carrying a steady current I within a uniform magnetic field B. It is specifically used when the conductor is rigid and the orientation relative to the field is known.
Why it matters: This principle is the core mechanism behind electric motors, which convert electrical energy into kinetic energy. It is also essential for the design of analog meters, loudspeakers, and electromagnetic particle accelerators.
Avoid these traps
Common Mistakes
- Mixing up direction rules.
- Using charge formula instead of current.
One free problem
Practice Problem
A straight wire of length 0.8 meters carries a current of 5.0 A. It is positioned perpendicular (90°) to a uniform magnetic field of 0.2 T. Calculate the magnetic force acting on the wire.
Solve for:
Hint: Since the wire is perpendicular, sin(90°) equals 1, meaning the force is simply the product of B, I, and L.
The full worked solution stays in the interactive walkthrough.
References
Sources
- Halliday, Resnick, Walker, Fundamentals of Physics
- Wikipedia: Lorentz force
- Britannica: Lorentz force
- Wikipedia article 'Lorentz force'
- Halliday, Resnick, Walker, Fundamentals of Physics, 10th Edition
- Wikipedia: Earth's magnetic field
- Wikipedia: Mains electricity
- Standard curriculum — A-Level Physics