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PowerPoint Lectures for
University Physics, Twelfth Edition
Hugh D. Young and Roger A. Freedman
Lectures by James Pazun
Chapter 28
Sources of MagneticField
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Goals for Chapter 28
To study the magnetic field generated by a moving
charge To consider magnetic field of a current-carrying
conductor
To examine the magnetic field of a long, straight,current-carrying conductor
To study the magnetic force between current-
carrying conductors
To consider the magnetic field of a current loop
To examine and use Amperes Law
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Introduction
Normally, when someone
describes a solenoid, theyare likely to use a
doorbell or car-starter as
their example. In the
photo at right, scientists atCERN are using the most
powerful magnetic field
ever proposed.
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The magnetic field of a moving charge
A moving charge will
generate a magnetic fieldrelative to the velocity of the
charge.
See Figure 28.1 at right.
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Moving chargesfield lines
The moving charge
will generate fieldlines in circles around
the charge in planes
perpendicular to the
line of motion.
Follow Example 28.1.
Refer to Figure 28.2.
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Magnetic field of a current element
The magnetic field of several
moving charges will be the
vector sum of each field.
Refer to Figure 28.3 at right.
Consider Problem-Solving
Strategy 28.1.
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Magnetic field of a current element II
Follow Example 28.2 and Figure
28.4 below.
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Magnetic field of a straight current-carrying conductor
Biot and Savart contributed to finding the magneticfield produced by a single current-carrying conductor.
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Fields around single wires
Refer to Example 28.3.
Refer to Example 28.4. Figure 28.7 illustrates
Example 28.4.
These apply to wires like the
one at right in Figure 28.8.
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Forces and parallel conductors
This is a classicdemonstration. When you
run the current one waythrough one rod and theother way through thesecond, they will snap
together. If you reverse theconnections on one rod sothat both currents run thesame way, the rods will flyapart.
Follow Example 28.5.
Figure 28.9 illustrates thisconcept.
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Magnetic field of a circular current loop
A loop in the x,y plane will experience magneticattraction or repulsion above and below the loop.
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Magnetic fields in coils
Consider Figures 28.13, 28.14, and 28.15 below.
Follow Example 28.6.
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Amperes Law Ispecific then general
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Amperes Law II
Consider Figure 28.18.
Follow Problem-SolvingStrategy 28.2.
Follow Example 28.7.
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Field inside a long cylindrical conductor
A cylinder of radius R carrying a current I.
Refer to Example 28.8 and Figure 28.20 and Figure 28.21.
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Field of a solenoid
A helical winding of wire on a cylinder.
Refer to Example 28.9 and Figures 28.2228.24.
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Field of a toroidal solenoid
A doughnut-shaped solenoid.
Refer to Example 28.10 and Figure 28.25.
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Magnetic materials
The Bohr magneton will determine how toclassify material. Refer to Figure 28.26
below. Follow Example 28.11. Ferromagnetic, paramagnetic, and
diamagnetic will help us designate materialthats naturally magnetized or magnetizable,material that can be influenced by a magnetic
field, and finally, material that is notinteractive with a magnetic field. Table 28.1at right will aid any calculation.
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Magnetic materials II
Consider Figure 28.27at right.
Consider Figure 28.28below.
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Magnetic materials III
Consider Figure 28.29 below.
Follow Example 28.12.
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