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Transformer Lesson 1

Magnetism and Electromagnetism

1) ? is a force that acts at a distance and is caused by a magnetic field. A. Magnetism
2 ) A(n) ? is easily magnetized. C. ferromagnetic material
3) A ? can hold its magnetism for a long period of time. A. permanent magnet
4) All magnets have a north and south pole. A. True
5) Unlike magnetic poles attract. A. True
6) The force of attraction between two magnets decreases as the distance between the magnets increases. A. True
7) A material is magnetic if it has ? . D. organized molecular magnets so that the individual fields add together
8) Permanent magnets might be demagnetized by a sharp blow. A. True
9) Permanent magnets might be demagnetized by extreme cold. B. False
10) ? is magnetism produced when electricity passes through a conductor. A. Electromagnetism
11) The left-hand rule can be used to determine the polarity of a coil. A. True
12) ? is the amount of magnetomotive force distributed over the length of a magnet. B. Magnetic field intensity
13) Match the magnetic unit of measure that it is analogous (similar in some respect) to. Magnetomotive Force = Voltage Field Flux = Current Reluctance = Resistance
14) Permeability is a measure of the ability of a material to conduct magnetic flux. A. True
15) The reference permeability of pure iron is 6,000 – 8,000; this means it has the ability to conduct magnetic flux better than copper. A. True
16) Copper is a ferromagnetic material. B. False
17) Cobalt is a ferromagnetic material. A. True
18) Nickel is a ferromagnetic material. A. True
19) Given the information in the Relative Permeability Chart, ? should be used as a transformer core to get the highest flux density for a given input before saturation occur. D. Pure Iron
20) Magnetic permeability is nonlinear. A. True
21) Saturation is where a magnetic core has substantially all the magnetic domains aligned with the field and any increases in current no longer result in a stronger electromagnet. A. True
22) When a magnetic circuit reaches a point of saturation, ? . C. Further increases in flux density are not possible
23) On a graph of a normal magnetization curve, which properties are represented on the two axes. A. I. and II.
24) Each normal magnetization curve, or B-H curve, has a knee where increases in the field strength no longer have much effect on the magnetic flux density. As more magnetic flux gets forced into the same area, more magnetic domains are available... B. False
25) Transformers are normally operated at the point of saturation. B. False
Created by: kwineinger13