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