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Magnetism

Electromagnetism, Magnetism

QuestionAnswer
Define electromagnetism. The branch of physics that deals with the relationship between electricity and magnetism.
What did OERSTED discover in 1820? That a magnetic field always surrounds a conductor in which a current is flowing.
Define helix. Coil of wire.
Define solenoid. Helix with electric current flowing through it.
Define electromagnet. A solenoid with an iron core inside it.
What are the four factors that regulate the strength of induced current under the The First Law of Electromagnetics? STRENGTH of magnetic field; SPEED of motion; ANGLE between magnetic lines of force; NUMBER OF TURNS in conducting coil.
Define self-induction. Induction of an opposing emf in a single coil by its own changing magnetic field.
Define mutual-induction. Inducing current flow through SECONDARY coil by passing varying current through primary coil.
Define magnetism. Ability of certain materials to attract iron, cobalt, nickel.
What are the 3 classes of magnets? Natural, Artificial Permanent, Electromagnet
Name an example of a natural magnet. Earth, Lodestone
Name an example of a artificial permanent magnet. Alnico, Hard steel
What are the 3 Laws of Magnetism? Every magnet has 2 poles; like repells-opposite attracts; the inverse square law
Define magnetic field. Zone of influence.
Define magnetic permeability. Ease with which a given material can become magnetized.
Define magnetic retentivity. Ability of magnet to resist demagnetization.
Soft iron has __ permeability, __ retentivity. High, low
Hard iron has __ permeability, __ retentivity. Low, high
What are the 4 magnetic classes of matter? Diamagnetic, Ferromagnetic, Nonmagnetic, Paramagnetic
Give examples of ferromagnetic materials. Iron, Cobalt, nickel
Give an example of paramagnetic materials. Platinum
Give examples of nonmagnetic materials. Glass, plastic, wood
Give examples of diamagnetic materials. Water, Bismuth
List characteristic of nonmagnetic matter. Unaffected by a magnetic field.
List characteristic of diamagnetic matter. Weakly repelled from both poles of magnetic field.
List characteristic of paramagnetic matter. Weakly attracted to both poles of magnetic field.
List characteristic of ferromagnetic matter. Can be strongly magnetized.
Name one of four factors that determine electromagnetic induction. SPEED that a conductor cuts magnetic lines of force.
Name one of four factors that determine electromagnetic induction. STRENGTH between conductor and direction of magnetic field.
Name one of four factors that determine electromagnetic induction. ANGLE between conductor and direction of magnetic field.
Name one of four factors that determine electromagnetic induction. NUMBER OF TURNS in conductor if wound into coil.
What is an electric motor? Device that converts electrical energy into mechanical energy.
What type of rings does a DC motor use? Commutator rings
What type of rings does an AC motor use? Slip rings
What are the 2 major types of AC motors? Synchronous and A-C Induction
What is a stator? Consists of pairs of stationary magnets arranged around the rotor.
Name an example of an electromagnet. Junkyard magnet used to move cars.
Describe the synchronous motor. Supplied by AC, built like single-phase AC generator. Speed must be synchronous with speed of generator.
Describe the induction motor. Has stator with even number of electromagnets. Has rotor in middle.
What is an electric generator? Device converting mechanical energy to electrical energy by electromagnetic induction.
Define magnetic domain. An accumulation of many atomic magnets with their dipoles aligned.
Define magnetic susceptibility. The degree to which a material can be magnetized.
Magnetic field Force field created when magnetic dipoles orient to create a magnet.
T/F: A magnetic field exists around a wire only while an electric current is flowing. True
Ammeter Current-measuring device.
Primary coil 1st coil through which varying current is passed.
Secondary coil 2nd coil containing induced current.
Lines of force always flow from N to S ____ a magnet and from S to N _____ a magnet. Outside, Within
Generator Device that converts mechanical energy to electrical energy.
Define motor. Device that is supplied with electrical current to produce mechanical motion.
What type of current does a galvanometer use? DC
What type of current does a dynamometer use? AC
Ammeter Meter connected in series that measures amps
Voltmeter Meter connected in parallel that measures potential difference.
T/F: Autotransformers are not suitable for use in high-voltage transformers in x-ray machines. True
What is the purpose of the autotransformer? To vary incoming-line voltage to an appropriate level for high-voltage step-up transformers.
What is the purpose of a high-voltage step-up transformer? To raise the incoming-line voltage to the kilovoltage range necessary for x-ray production.
What is the purpose of the filament step-down transformer? To decrease the incoming-line voltage to 5-15 volt range used to heat the x-ray tube filament.
The flow of electrons is known as what? Current
What effect does a low temperature have on resistance? Decreases
Maximum induction will occur when a conductor cuts a magnetic field at what angle? 90 degrees
What happens when a wire moves through a megnetic field? An emf is induced
Created by: rad1958tech on 2008-02-17



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