Magnetism and Electrodynamics Flashcards

Flashcards about Magnetism and Electrodynamics

Electrodynamics

The field of physics that deals with the relationships between electricity and magnetism, specifically change and motion.

Electromagnet

A magnet that consists of a coil of wire, usually wound around a core of iron or other ferromagnetic material. It produces a magnetic field only when an electric current flows through the wire.

Magnetic Poles

The two points or regions of a magnet, called the north pole and the south pole, where the magnetic field is strongest. Like poles repel each other, and opposite poles attract each other.

Magnetostatic Forces

The forces between magnetic poles, which are attractive or repulsive depending on whether the poles are opposite or like. The forces decrease with distance.

Magnetic Monopoles

Hypothetical subatomic particles that carry a pure north or south magnetic pole. They are theorized to exist, but have not been observed.

Magnetic Dipole

A pair of equal north and south magnetic poles, spatially separated from one another. A simple button magnet is an example.

Ampere-meter (A·m)

The SI unit of magnetic pole.

Ferromagnetic Material

A material, such as iron or ordinary steel, that is actively and unavoidably magnetic on the scale of atoms.

Magnetic Domains

Microscopic regions within a ferromagnetic material where atomic-scale magnetic dipoles are aligned, giving the domain a substantial net magnetic dipole.

Domain Walls

Boundary surfaces between magnetic domains that must move for the domains to change size, but can be impeded by flaws or impurities in the material.

Soft Magnetic Material

A material (e.g., chemically pure iron) that demagnetizes itself easily when all nearby poles are removed; easy to magnetize and demagnetize.

Hard Magnetic Material

A material that does not demagnetize itself easily and tends to retain whatever domain structure is imposed on it; used to make permanent magnets.

Magnetic Field

An attribute of space that exerts a magnetostatic force on a pole; it can be created by magnetic poles or by moving electric charges.

Tesla (T)

The SI unit of magnetic field, equivalent to newton per ampere-meter (N/A·m).

Magnetic Flux Lines

Strands that map the magnetic field. They point along the local magnetic field direction and have a density proportional to that local field.

Electromagnet

A device that becomes magnetic when it carries an electric current. It concentrates and strengthens the magnetic field.

Alternating Current (AC)

Electric current in which the flow of electric charge periodically reverses direction.

Direct Current (DC)

Electric current that flows in one direction only.

Electrical Resistance

A property of a wire that impedes the flow of electric current.

Magnetic Induction

The process whereby a time-changing magnetic field initiates or influences an electric current.

Lenz’s Law

When a changing magnetic field induces a current in a conductor, the magnetic field from that current opposes the change that induced it.

Inductor

A wire coil's natural opposition to current change that makes it quite useful in electrical equipment and electronics.

Back Emf (Electromotive Force)

A coil's self-induced emf (electromotive force) that is responsible for bouncing energy back to the current.

Transformers

A device that is used to transfer electric power from one AC circuit to another. They use two important connections between electricity and magnetism to convey power from one AC circuit to another.

Magnetic Fields

Contains energy and can be calculated with the following equation: energy = (magnetic field2 * volume) / (2 * permeability of free space)

RMS (Root Mean Square)

Defines an effective voltage for AC electric power and is defined to be equal to the DC voltage that would cause the same average power consumption in an ohmic device.

Generator

A device that extracts mechanical power from machinery and delivers electric power to a circuit.

Motor

A device that extracts electric power from a circuit and delivers mechanical power to machinery.