Magnetic Field

1
Ch. 29 Sources of Magnetic Fields
Ch29-1
B-Field due to Currents

• Magnetic Field

B-field due to single moving charge ? current
(segment, straight wire, loop, solenoid) ?
Amperes law ? magnetic properties of matter
Biot-Savart Law
B-Field of Moving Point Charges
B-field due to Current Loop
(Ex 29-2)
(Ex 29-1)
2
B-Fields due to a Current-I
Ch29-2
B-Field Lines due to I in a Solenoid
B-Field due to a Current in a Solenoid
Field lines due to 2 loops carrying the same
current in the same sense
B-Field due to a Current in a Straight Wire
3
B-Fields due to a Current-II
Ch29-3
(Ex 29-5)
Forces between two straight wires (Rail gun)
(Ex 29-6)
Gausss Law for Magnetism
4
Amperes Law
Ch29-4
Toroid
Amperes Law
(Ex 29-8)
Solenoid
5
Magnetism in Matter-I
Ch29-5
Atomic Magnetic Moment
Atomic Magnetic Moments

• Orbital magnetic moment (e- motion)
• Spin magnetic moment of e-

Materials in View of Magnetism
Paramagnet, Diamagnet, Ferromagnet
Magnetization
Paramagnetism
Mag. Susceptibility
The atoms have magnetic dipole moment. If Bapp0,
dipoles are randomly oriented. If B?0, ?mgt0
6
Magnetism in Matter-II
Ch29-6
Diamagnetism
The atoms have no magnetic dipole moment. If B?0,
?mlt0
Ferromagnetism
Fe, Co, Ni and their alloys Gd, Dy and a few
compound Exchange interaction between spins
Weisss assumption
molecular field
Magnetic domain
7
Magnetic Recording
8
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