ch 28 lecture

8/3/2019 Ch 28 Lecture

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Copyright 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley

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.



Magnetic field of a straight current-carrying conductor

Biot and Savart contributed to finding the magneticfield produced by a single current-carrying conductor.



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.



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.


Figure 28.9 illustrates thisconcept.



Magnetic field of a circular current loop

A loop in the x,y plane will experience magneticattraction or repulsion above and below the loop.



Magnetic fields in coils

Consider Figures 28.13, 28.14, and 28.15 below.




Amperes Law Ispecific then general


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Amperes Law II

Consider Figure 28.18.

Follow Problem-SolvingStrategy 28.2.



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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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Copyright 2008 Pearson Education Inc publishing as Pearson Addison-Wesley

Magnetic materials III

Consider Figure 28.29 below.


ch 28 lecture

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