Glossary
Diamagnetism
A property of materials that are weakly repelled by magnetic fields, as their electronic structure creates a magnetic moment that opposes the external field.
Example:
A powerful superconducting magnet can levitate a strawberry due to the diamagnetism of the water molecules within it.
Electromagnetic induction
The process by which a changing magnetic flux through a conductor or circuit induces an electromotive force (emf) and, if the circuit is closed, an electric current.
Example:
Generators convert mechanical energy into electrical energy through electromagnetic induction, as rotating coils experience a changing magnetic flux.
Faraday's Law
States that the magnitude of the induced electromotive force (emf) in a circuit is directly proportional to the rate of change of magnetic flux through the circuit.
Example:
According to Faraday's Law, rapidly moving a strong magnet through a coil of wire will induce a larger voltage than moving a weak magnet slowly.
Ferromagnetism
A property of materials that can become permanently magnetized due to the alignment of their internal magnetic domains when exposed to an external magnetic field.
Example:
An electromagnet often uses an iron core, a ferromagnetic material, to significantly amplify the magnetic field it produces.
Induced Current
The electric current that flows in a conductor or circuit as a result of an induced electromotive force, driven by a changing magnetic flux.
Example:
If you quickly pull a magnet out of a coil connected to a galvanometer, the deflection of the needle indicates an induced current flowing through the coil.
Induced EMF
The electromotive force (voltage) generated across a conductor or circuit due to a changing magnetic flux, which can drive an induced current if the circuit is closed.
Example:
When a car's engine is running, the alternator generates an induced EMF to recharge the car's battery.
Lenz's Law
States that the direction of the induced current (and its associated magnetic field) will always oppose the change in magnetic flux that caused it, ensuring energy conservation.
Example:
If you drop a strong magnet down a copper pipe, Lenz's Law explains why it falls slowly, as the induced currents create a magnetic field that opposes the magnet's motion.
Magnetic Flux
A measure of the total number of magnetic field lines passing through a given area, calculated as the product of the magnetic field strength perpendicular to the area and the area itself.
Example:
When a metal detector sweeps over a buried coin, the changing magnetic flux through its coil indicates the presence of metal.
Magnetic domains
Microscopic regions within ferromagnetic materials where the atomic magnetic dipoles are aligned, creating a net magnetic moment within that region.
Example:
Heating a permanent magnet above its Curie temperature can disrupt its magnetic domains, causing it to lose its magnetism.
Paramagnetism
A property of materials that are weakly attracted to magnetic fields; their magnetic dipoles temporarily align with the external field but return to a random orientation once the field is removed.
Example:
Liquid oxygen is paramagnetic, which is why it can be weakly suspended between the poles of a strong magnet.