Magnetic force

Definition

Magnetic force is the force experienced by a moving charge in a magnetic field. It acts perpendicular to both the velocity of the charge and the magnetic field direction.

5 Must Know Facts For Your Next Test

1. The magnitude of the magnetic force on a moving charge is given by $F = qvB\sin(\theta)$, where $q$ is the charge, $v$ is the velocity, $B$ is the magnetic field strength, and $\theta$ is the angle between the velocity and the magnetic field.
2. Magnetic force does no work on a moving charge as it always acts perpendicular to the direction of motion.
3. A positively charged particle will experience a force in one direction, while a negatively charged particle will experience it in the opposite direction under identical conditions.
4. The direction of the magnetic force can be determined using the right-hand rule: Point your thumb in the direction of velocity (for positive charges) or opposite (for negative charges), your fingers in the direction of $B$, and your palm points in the direction of force.
5. When a charged particle moves parallel or anti-parallel to a magnetic field line ($\theta = 0^\circ$ or $180^\circ$), it experiences no magnetic force.

Review Questions

• What factors determine the magnitude of the magnetic force on a moving charge?
• Why does magnetic force not perform work on a charged particle?
• How can you use the right-hand rule to find the direction of magnetic force?

Related terms

Lorentz Force:

The total force exerted on a charged particle due to electric and magnetic fields, given by $$F = q(E + v \times B)$$.

Right-Hand Rule:

A mnemonic for understanding orientation conventions for vectors in three dimensions; used to determine directions of axes or forces.

Magnetic Field:

A vector field surrounding magnets and electric currents, represented by $B$, that exerts forces on moving charges.