Download Study Guide - Chapter 29

Magnetic Fields
Study Guide for Chapter 29
Outline
1. Magnetic Fields and Forces
The main formula is the law for the magnetic force on a moving charge:
t œ ; tv ‚ B
t
F
t is the magnetic field, and ‚ represents the
Here ; is the charge, tv is the velocity of the charge, B
cross product of vectors.
This section also introduces the tesla T, which is the SI unit for magnetic fields:
"T œ "
N
N
œ "
C † m Îs
A†m
Problems: 1, 3, 5, 7, 49
2. Motion of a Charged Particle in a Uniform Magnetic Field
t will move in a circle (determined by the rightA charged particle in a uniform magnetic field B
hand rule). The radius, angular velocity, and period of the circular motion are:
<œ
7@
ß
;F
=œ
;F
ß
7
X œ
#1 7
;F
t, the path will be a helix instead.
If the particle is also moving parallel to B
Problems: 9
3. Applications Involving Charged Particles Moving in a Magnetic Field
This section discusses several real-world applications of using magnetic fields to affect the
motion of charged particles. You should read and understand this section, but you will not be
required to know the details of the applications.
4. Magnetic Force Acting on a Current-Carrying Conductor
A segment of current-carrying wire in a uniform magnetic field experiences the following force:
tœML
t‚B
t
F
t is the magnetic field, and L
t is the length vector of the wire:
Here M is the current in the wire, B
t is the vector that points from the beginning of the wire to the end of the wire.
L
t œ t0, and therefore the net magnetic force on a closed loop of wire
A closed loop of wire has L
in a uniform magnetic field is always zero.
Problems: 25, 27
5. Torque on a Current Loop in a Uniform Magnetic Field
Though the net force on a loop of wire in a uniform magnetic field is always zero, a magnetic
field can exert torque on a loop of wire. This is given by the equation:
t
t‚B
7t œ .
t is called the magnetic moment. It is defined as follows.:
The vector .
t is ME, where M is the current, and E is the area of the loop.
The magnitude of .
t is determined by the right-hand rule.
The direction of .
Problems: 34, 35, 37
Answers: #34 (a) &Þ%" ‚ "!$ N † mÎT (b) %Þ$$ ‚ "!$ N † m
6. The Hall Effect
This section explains how it was discovered that the current carriers in a wire are negatively
charged. You should read and understand this section.