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Magnetism
Electromagnetism, Magnetism
| Question | Answer |
|---|---|
| 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
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