Chap. 5. Magnetic Properties - KOCw

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부산대학교 재료공학부 [Magnetic Properties] 계면공학 연구실

Chap. 5. Magnetic Properties

 Magnetism is a class of physical phenomena that are mediated by magnetic fields. Electric currents and the fundamental magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments.

Spin and orbital motion of electrons

Operation principle

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부산대학교 재료공학부 계면공학 연구실

 Hysteresis loop

 Magnetization [demag- ]

B[M]-H loop:

B = H + 4πM

[Hysteresis Loop]

H: applied magnetic field

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부산대학교 재료공학부 [Hysteresis Loop] 계면공학 연구실

Hysteresis loop: Magnetization [demagnetization] in materials

 Hard magnetic- : permanent magnet

 Soft magnetic- : recording materials

Magnetic domain: the area of same spin alignment region

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 Principle of Magnetic recording

 Recording [Reading] of 0/1

[Magnetic Recording /Reading]

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부산대학교 재료공학부 [Microphone and Speaker] 계면공학 연구실

[Microphone] [Speaker]

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Lenz's law /ˈlɛnts/ is a common way of understanding how

electromagnetic circuits obey Newton's third law and the conservation of energy.

If an induced current flows, its direction is always such that it will oppose the change which produced it. Lenz's law is shown with the negative sign in

Faraday's law of induction:

which indicates that the induced voltage (ℰ) and the change in magnetic flux (∂Φ) have opposite signs.

 Principle of Generator and Motor by using Fleming’s Right/Left Rule

[Principle of Generator / Motor]

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Notation:

direction of current and

direction of magnetic field

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부산대학교 재료공학부 [Principle of Generator / Motor] 계면공학 연구실

Understanding of Fleming’s Left Hand Rule for Motor [

전동기

]

[N  S]

[ +  -]

[conductor]

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 Force attraction and repulsion of conductor in the magnetic field

 Motion of conductor (coiled body) [  Motor]

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 Motion of conductor (single-turn coil) [  Motion of rotor]

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 Motion of conductor (multi-turn coil) [  Motion of rotor]

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How can we rotate the rotator?

 Boiled water, wind, falling water?

[

수력

,

풍력

,

화력

,

원자력

]

발전기

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 Electro Motive Force (EMF) generation by Rotational Conductor[Coil]

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부산대학교 재료공학부 [Principle of Generator/ Motor] 계면공학 연구실

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[Homework #5] / Due date: before next class

1. Describe principle of microphone in terms of magnet.

2. Describe principle of speaker in terms of magnet.

3. Describe principle of magnetic recording in terms of magnet.

4. Describe principle of magnetic reading in terms of magnet.

5. Describe principle of electric motor in terms of magnet.

6. Describe principle of electric generator in terms of magnet.

[Magnetic Properties]