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Transformers ch 1

Magnetism and Electromagnetism

QuestionAnswer
1. ___ is a force that acts at a distance and is caused by a magnetic field Magnetism
2. A ___ is a material that is easily magnetized . ferromagnetic material
3. A ___ is a magnet that can hold its magnetism for a long period of time. permanent magnet
4. All magnets have a north and south pole. True/False True
5. Unlike magnetic poles attract. True/False True
6. The force of attraction between two magnets decreases as the distance between the magnets increases. True/False True
7. A material is magnetic if it has __ ( multiple choice) organized molecular magnets so that the individual fields add together
8. Permanent magnets may be demagnetized by a sharp blow. True/False True
9. Permanent magnets may be demagnetized by extreme cold. True/False False. Heat
10. ___ is magnetism produced when electricity passes through a conductor. multiple choice Electromagnetism
11.The left-hand rule can be used to determine the polarity of a coil. Draw a picture of the left hand rule.. True/False True
12. ___ is the amount of magnetomotive force distributed over the length of a magnet. multiple choice Magnetic field intensity
13. List the magnetic units of measure that are analogous to: voltage, current, resistance Voltage = Magnetomotive force measured in "AMP-TURN" ; Current = Magnetic Flux measured in "LINE" Resistance= Reluctance measured in AMP-TURNS PER LINE
14. Permeability is a measure of the ability of a material to conduct magnetic flux True/False True
15. The reference permeability of pure iron is 6000 - 8000. Does this mean it has the ability to conduct electricity better or worst than copper? Neither
16.Copper is a ferromagnetic material. True/False False
17. Cobalt is a ferromagnetic material. True/False True
18. Nickel is a ferromagnetic material. True/False True
19. Given the Relative Permeability chart, ___ should be used as a transformer core to get the highest flux density for a given input before saturation occurs. (copper, nickel, ferrite, or pure iron) pure iron
20. Magnetic permeability is nonlinear. True/False True
21. Explain magnetic saturation
22. When a magnetic circuit reaches a point of saturation, ___ (multiple choice) further increases in flux density are not possible
23. On a graph of a normal magnetization curve, what properties are represented on the two axes? what is another name for this type of graph? field intensity and flux density, BH curve
24. Explain the significance of the knee in a normal magnetization curve. Once the knee is passed there is a lot of field intensity but not much in flux density
25. Transformers are normally operated at the point of saturation. True/False False
Created by: JoshHampton
 

 



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