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Magnetism (sec. 27.1) Magnetic field (sec. 27.2) Magnetic field lines and magnetic flux (sec. 27.3) Motion of charges in a B field (sec. 27.4) Applications - moving charged particles (sec. 27.5) Magnetic force on
conductor with current (sec. 27.6) Force and torque on a current loop (sec. 27.7) Direct current motor (sec. 27.8) The Hall effect (sec. 27.9)
Magnetic Field & Forces Ch. 27
C 2009 J. Becker
Magnetic field lines associated with a permanent magnet, coil, iron-core electromagnet, current in
wire, current loop
Mass spectrometer uses a velocity selector to produce particles with uniform speed.
And from R = m v / q B
we get
q / m = v / B R
Force on a moving positive charge in a
current-carrying conductor:
F = I L x BL
I
I
For vector direction use “RIGHT HAND
RULE”
Magnetic force on a straight wire carrying current I in a magnetic field B
Right hand rule
F = I L x B
Forces on the sides of a current-carrying loop in a uniform magnetic field.
This is how a motor works!
Torque ( x B) on this solenoid in a uniform magnetic field is into the screen
thus rotating the solenoid clockwise
Atomic magnetic moments in an iron bar
(a) unmagnetized
(b) magnetized
(c)Torgue on a bar magnet in a B field
Bar magnet attracts an unmagnetized piece of iron; the B field gives rise to
a net magnetic moment in the object
The Hall effect – forces on charge carriers in a conductor in a B field.
With a simple voltage measurement we can determine whether the “charge carriers” are
positive or negative.