Question	Answer
alternating current	An electrical current that periodically changes direction at a specific frequency.
brush	One of the many curved blocks of conductive material that ride on a rotor commutator to connect the rotor coils to the external electrical circuit.
Curie temperature	The temperature at which a permanent magnet loses its magnetic field.
diamagnetism	The natural tendency of all matter to weaken a magnetic field, especially in the absence of other kinds of magnetism. These materials generate a magnetic field that opposes the external magnetic field.
Domains	Microscopic regions of materials that may be lined up in a single direction to produce a magnetic field of force.
electromagnet	A solenoid with a ferromagnetic core.
electromagnetic induction	Electricity generated from a changing magnetic field or a magnetic field generated by an electrical current.
ferrimagnetism	A form of magnetism that results from the net difference of a mixture of opposed magnetic dipole particles in a natural magnet, such as a lodestone.
ferromagnetic material	A material that naturally has ferromagnetism.
geographic north pole	The point representing the intersection of the earth’s axis with its surface in the northern hemisphere. All lines of longitude pass through this point. Also called true north.
hertz (Hz)	The SI unit of frequency’ one cycle per second.
law of magnetism	A law that says like magnetic poles attract and opposite magnetic poles repel.
magnetic dipole	Any object or particle with magnetic properties, i.e., having two magnetic poles. All magnets are magnetic dipoles.
paramagnetism	Exhibited by materials that are only slightly attracted to magnets. It varies with temperature and does not produce permanent magnets.
permanent magnet	A ferromagnetic material containing enough aligned magnetic domains to give it a permanent magnetic character.
rotor	Part of an electrical motor or generator that rotates. Depending on the application, it may include permanent magnets or electromagnets.
Solenoids	An electromagnetic device consisting of a cylinder formed by many wraps of wire. When carrying a current, a strong magnetic field forms within the cylinder of wire.
stator	The stationary part of an electrical motor or generator thatcontains the magnets or induction coils that surround the rotor.
superconducting magnet	A magnet made from special materials that have zero resistance to current flow and kept at extremely low temperatures.
transformer	An electrical device used in AC circuits consisting of two coils of wire wound on a single ferromagnetic core, usually shaped like a hollow square. It can either raise or lower the voltage in an AC circuit.
turbine	Any mechanical device that converts fluid motion into rotary motion as the fluid passes through propeller-like blades.
commutator	A device that converts the alternating current inside a DC generator to a DC output or converts a DC supply to an alternating current inside a DC motor.
ferromagnetism	The phenomenon observed in materials that are highly permeable to magnetic lines of force because their magnetic domains align with the field, reinforcing it.
geomagnetic field	The magnetic field of the earth.
magnet	An object that possesses or can have a magnetic field
magnetic field	The region of influence surrounding a magnet, where it exerts a magnetic field which is shown by lines of force.
magnetic North pole	The slowly drifting point on the earth’s surface in the northern hemisphere where the earth’s magnetic field lines are most concentrated and nearly vertical as they pass into the earth’s interior; the south magnetic pole of the earth’s geomagnetic field.
magnetic pole	One of two areas of concentrated magnetic field lines on a magnet’s surface. The field direction for each pole is the opposite of the other.
motor	A machine that converts electrical energy into rotational mechanical motion.
right-hand rule of magnetism	Rule that the direction of the magnetic field surrounding a current-carrying conductor is indicated by the direction the right hand fingers wrap around the conductor, the thumb pointing in the direction of the conventional current flow.

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