Magnetic Field

1
Ch. 28 The Magnetic Fields
Ch28-1

• Magnetic Field

• field
• out of page

• Source for magnetic fields
• Electromagnet
• Permanent magnet
• Reason for magnetic field
• Moving charges such as current
• Intrinsic property of particles (spin)

Def. of magnetic field
(Ex 28-1)
z
y
x
2
FB on a Current-Carrying Wire
Ch28-2
For straight wire
(Ex 28-2)
In general
(Ex 28-3)
Magnetic field lines 1. Field lines are perp. to
magnetic force. 2. Magnetic field lines form
closed loop.
3
Motion of Charge in B-Field-I
Ch28-3
no dependence on v.
Mass Spectrometer
Velocity Selector
4
Motion of Charge in B-Field-II
Ch28-4
Discovery of Electrons -J. J. Thomson 1897-
Cycltron
5
Torque on Current Loops
Ch28-5
Torque on a Current Loop
(Ex 28-11)
Electric motor
Hall Effect -E. H. Hall 1879-
at equil.
(Hall Voltage)
Potential Energy of a Magnetic Dipole