Glossary
Ampere's Law
A fundamental law in electromagnetism that relates the circulation of a magnetic field around a closed loop to the electric current passing through the loop.
Example:
Using Ampere's Law, one can calculate the magnetic field inside a long solenoid or around a current-carrying wire.
Diamagnetic
Materials that are weakly repelled by magnetic fields, creating an induced magnetic field in the opposite direction of the applied field.
Example:
Water and copper are diamagnetic materials; a very strong magnet can cause them to levitate slightly due to the repulsive force.
Ferromagnetic
Materials that exhibit strong, permanent magnetism due to the spontaneous alignment of magnetic domains, even without an external magnetic field.
Example:
Iron, nickel, and cobalt are ferromagnetic materials, which is why they are commonly used to make strong permanent magnets.
Induced Magnetism
Temporary magnetism created in a material when it is placed within an external magnetic field, causing its magnetic dipoles to align temporarily.
Example:
When you pick up a paperclip with a strong magnet, the paperclip temporarily gains induced magnetism and can then pick up another paperclip, but loses it when the main magnet is removed.
Magnetic Dipole Moment
A measure of an object's tendency to interact with a magnetic field, representing the strength and orientation of a magnetic dipole.
Example:
An electron orbiting an atom creates a tiny magnetic dipole moment, contributing to the overall magnetic properties of the material.
Magnetic Permeability
A measure of how easily a material can be magnetized, indicating how much it allows magnetic field lines to pass through it.
Example:
A transformer core made of soft iron has high magnetic permeability, allowing it to efficiently concentrate magnetic field lines and transfer energy.
Paramagnetic
Materials that are weakly attracted to magnetic fields, where their magnetic dipole moments align temporarily with an external field but randomize when the field is removed.
Example:
Aluminum is a paramagnetic material; it will be very slightly attracted to a strong magnet, but won't retain any magnetism once the magnet is gone.
Permanent Magnetism
The phenomenon where a material retains its magnetic properties even after the external magnetic field is removed, due to aligned magnetic dipole moments.
Example:
A refrigerator magnet exhibits permanent magnetism because its internal dipoles remain aligned, allowing it to stick to the fridge door indefinitely.
Permeability of Free Space
A fundamental physical constant representing the magnetic permeability of a vacuum, used in many electromagnetism equations.
Example:
When calculating the magnetic field produced by a current in empty space, you'll always use the permeability of free space in the formula.
Permittivity
A measure of how an electric field affects, and is affected by, a dielectric medium, representing the ability of a material to store electrical energy in an electric field.
Example:
The permittivity of a material determines how much charge can be stored on the plates of a capacitor when that material is used as the dielectric.
Solenoid
A coil of wire typically wound into a tightly packed helix, which produces a nearly uniform magnetic field inside when current flows through it.
Example:
An electromagnet often uses a solenoid to generate a strong, controllable magnetic field by passing current through its coils.