Magnetism (sec. 27.1) Magnetic field (sec. 27.2) Magnetic field lines and magnetic flux (sec. 27.3)...
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Transcript of Magnetism (sec. 27.1) Magnetic field (sec. 27.2) Magnetic field lines and magnetic flux (sec. 27.3)...
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.