CHAPTER 20

Magnetism

IN THIS CHAPTER
Summary: Magnetic fields produce forces on moving charges; moving charges, such as current-carrying wires, can create magnetic fields.
This chapter discusses the production and the effects of magnetic fields.

Key Ideas
The force on a moving charge due to a magnetic field is qvB .
The direction of the magnetic force on a moving charge is given by a right-hand rule, and is NOT in the
direction of the magnetic field.
Current-carrying wires produce magnetic fields.
When the magnetic flux through a wire changes, a voltage is induced.
An inductor inhibits the change in the current running through it. After a long time, the inductor acts as a
bare wire.

Relevant Equations

Force on a charged particle in a magnetic field:

F = qvB

Force on a current-carrying wire:

F = ILB

Magnetic field due to a long, straight, current-carrying wire:

Magnetic flux:

Φ (^) B = BA