Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2...
Transcript of Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2...
![Page 1: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/1.jpg)
ISU EE C.Y. Lee
Chapter 7Magnetism and
Electromagnetism
![Page 2: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/2.jpg)
2ISU EE C.Y. Lee
Objectives
Explain the principles of the magnetic fieldExplain the principles of electromagnetismDescribe the principle of operation for several types of electromagnetic devicesDiscuss the principle of electromagnetic inductionDescribe some applications of electromagnetic induction
![Page 3: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/3.jpg)
3ISU EE C.Y. Lee
The Magnetic FieldA permanent magnet has a magnetic field surrounding itA magnetic field is envisioned to consist of flux lines that radiate from the north pole to the south pole and back to the north pole through the magnetic material
![Page 4: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/4.jpg)
4ISU EE C.Y. Lee
Attraction and RepulsionUnlike magnetic poles have an attractive force between them
Two like poles repel each other
![Page 5: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/5.jpg)
5ISU EE C.Y. Lee
Altering a Magnetic FieldWhen nonmagnetic materials such as paper, glass, wood or plastic are placed in a magnetic field, the lines of force are unaltered
![Page 6: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/6.jpg)
6ISU EE C.Y. Lee
Altering a Magnetic FieldWhen a magnetic material such as iron is placed in a magnetic field, the flux lines tend to be altered to pass through the magnetic material
![Page 7: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/7.jpg)
7ISU EE C.Y. Lee
Magnetic FluxThe force lines going from the north pole to the south pole of a magnet are called magnetic flux (φ); units: weber (Wb)The magnetic flux density (B) is the amount of flux per unit area perpendicular to the magnetic field; units: tesla (T)
1 T = 10000 G (Gauss)
AB φ=
![Page 8: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/8.jpg)
8ISU EE C.Y. Lee
Magnetic Flux
AB φ=
Example: Find the flux density in a magnetic field in which the flux in 0.1 m2 is 800 μWb
TmWb
AB μμφ 8000
10800
2 ===.
![Page 9: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/9.jpg)
9ISU EE C.Y. Lee
Magnetizing Materials
Ferromagnetic materials such as iron, nickel and cobalt have randomly oriented magnetic domains, which become aligned when placed in a magnetic field, thus they effectively become magnets
![Page 10: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/10.jpg)
10ISU EE C.Y. Lee
Application (Magnetic Switch)
Operation of a magnetic switch
Connection of a typical perimeter alarm system
![Page 11: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/11.jpg)
11ISU EE C.Y. Lee
Electromagnetism
The right-hand rule is used to determine the direction of the lines of force
Electromagnetism is the production of a magnetic field by current in a conductor
![Page 12: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/12.jpg)
12ISU EE C.Y. Lee
Electromagnetic FieldWhen current passes through a conductor, an electromagnetic field is created around the conductor
![Page 13: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/13.jpg)
13ISU EE C.Y. Lee
Electromagnetic DevicesElectromagnets are used in devices such as magnetic disk, electric motors, speakers, solenoids, and relays
Read/write function on a magnetic surface
![Page 14: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/14.jpg)
14ISU EE C.Y. Lee
Electromagnetic DevicesThe solenoid is used for applications such as opening and closing valves and automobile door locks
Basic solenoid operation:
![Page 15: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/15.jpg)
15ISU EE C.Y. Lee
Electromagnetic DevicesRelays differ from solenoids in that the electromagnetic action is used to open or close electrical contacts rather than to provide mechanical movement
Basic structure of a relay:
![Page 16: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/16.jpg)
16ISU EE C.Y. Lee
Electromagnetic DevicesPermanent-magnet speakers are commonly used in stereos, radios, and TVs, and their operation is based on the principle of electromagnetism
Basic speaker operation with movement:
![Page 17: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/17.jpg)
17ISU EE C.Y. Lee
Electromagnetic InductionWhen a conductor is moved through a magnetic field, a voltage is induced across the conductorThis principle is known as electromagnetic induction
The faster the relative motion, the greater the induced voltage
![Page 18: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/18.jpg)
18ISU EE C.Y. Lee
Relative MotionWhen a magnetic field is moved past a stationary wire, there is also relative motionThe induce voltage depends on the rate of relative motion between the wire and the magnetic field
![Page 19: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/19.jpg)
19ISU EE C.Y. Lee
Polarity of Induced VoltageThe direction of movement of a wire through a magnetic field will affect the polarity of the induced voltage as indicated below:
![Page 20: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/20.jpg)
20ISU EE C.Y. Lee
Induced CurrentThe voltage induced by the relative motion of a wire through a magnetic field will cause a current in a load connected to the wireThis current is called an induced current
![Page 21: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/21.jpg)
21ISU EE C.Y. Lee
Motor ActionWhen a current flows through a wire that is in a magnetic field, the direction of current flow will result in the magnetic field being weakened on one side, and strengthened on the otherThe result of the weakened and strengthened field is a force on the conductor
![Page 22: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/22.jpg)
22ISU EE C.Y. Lee
Faraday’s LawThe voltage induced across a coil of wire equals the number of turns in the coil times the rate of change of the magnetic flux
dtdN BΦ
−=ε
MOVIE ACTIVE
![Page 23: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/23.jpg)
23ISU EE C.Y. Lee
Lenz’s LawLenz’ Law states the polarity of the induced voltage in a loop is such that it produces a current whose magnetic field opposes the change in magnetic flux through the loop
![Page 24: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/24.jpg)
24ISU EE C.Y. Lee
DC GeneratorBasic operation of a dc generator
![Page 25: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/25.jpg)
25ISU EE C.Y. Lee
Summary
Unlike magnetic poles attract each other, and like poles repel each otherMaterials that can be magnetized are called ferromagneticWhen there is current through a conductor, it produces an electromagnetic field around the conductorThe right-hand rule can be used to establish the direction of the electromagnetic lines of force around a conductor
![Page 26: Magnetism and Electromagnetism - I-Shou · PDF fileMagnetism and Electromagnetism. ISU EE 2 C.Y. Lee Objectives Explain the principles of the magnetic field ... Discuss the principle](https://reader033.fdocuments.net/reader033/viewer/2022052709/5a79b5b47f8b9afa378be070/html5/thumbnails/26.jpg)
26ISU EE C.Y. Lee
Summary
When a conductor moves within a magnetic field, or when a magnetic field moves relative to a conductor, a voltage is induced across the conductorThe faster the relative motion between a conductor and a magnetic field, the greater is the induced voltageThe polarity of the induced voltage in a loop is such that it produces a current whose magnetic field opposes the change in magnetic flux through the loop