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Magnetism & EM
Questions from PPT
Question | Answer |
---|---|
What was the first magnet? | magnetite or lodestone |
What is the largest magnet? | Earth |
What is a battery? | source of electromagnetic force |
What is magnetism? | fundamental property of some forms of matter |
Describe magnetic field: | lines of force; indicate direction of magnetic force |
Describe electron motion: | rotate on own axis; clockwise or counterclockwise |
What is dipole? | each end has equal but opposite charges; North & South poles |
What is domain? | accumulation of dipoles |
Desribe lines of force: | inside magent: S-> N; outside magnet: N-> S |
What is permeability? | ability to become magnetized |
What is retentivity? | ability to remain magnetized |
Describe 3 classifications of magnets: | natural-earth or lodestone; artificial-bar magnet; electromagnet-wire around iron core |
Describe 4 states of matter: | nonmagnetic-unaffected; ferromagnetic-strongly attracted; paramagnetic-slightly attracted; diamagnetic-slightly repelled |
List the Laws of Magnetism: | 1-dipole, North & South poles; 2-like poles repel, unlike poles attract; 3-ferromagnetic material can be magnetized in external magnetic field; 4-intensity of field is directly related to magnetic pole strength & indirectly related to distance squared |
What is the unit of measure? SI? | gauss; tesla |
What is electromagnetism? | force associated with electrons in motion |
What are 3 ways of EM induction? | 1-move conductor across stationary magnetic field; 2-cut stationary conductor with magnetic lines of force; 3-stationary conductor in magnetic field with varying magnetic flux |
What is Faraday's Law? | electric current is induced to flow in circuit if part of circuit is in changing magnetic field |
What is Lenz's Law? | induced current flows opposite the action that induces it |
What is a helix? | coil of wire |
What is a solenoid? | coil of wire with a source and current |
What is an electromagnet? | coil of wire with source & current that is wrapped around an iron core |
Describe EM Self Induction: | coil of wire carries current & sets up current within itself |
Describe Autotransformer: | primary side of circuit; kVp selector; uses self induction |
Describe EM Mutual Induction: | primary coil-potential difference creates current; secondary coil-carries induced current |
Describe Step Up Transformer: | uses mutual induction; voltage to kVp; amperage to mA; more turns on secondary coil |
Describe Step Down Transformer: | uses mutual induction; kVp to voltage; mA to amperage; more turns on primary coil; filament current; secondary side of circuit |
What is a generator? | dynamo; converts mechanical to electrical energy |
What is a motor? | rotor; converts electrical to mechanical energy |
Describe Air Core Transformer: | solenoid |
Describe Open Core Transformer: | electromagnet |
Describe Closed Core Transformer: | electromagnet where iron cores are connected |
Describe Shell Core Transformer: | both coils of wire are wrapped around same iron core, iron core is laminated |