In the final chapter on electromagnetism we consider magnetic effects. Charges at rest
are electric field sources. You will soon find that charges in motion create magnetic
fields. Charges moving through magnetic fields will also react to the field if the
I
The value of B is determined by multiplying an ammeter reading by the geometrical
properties of the coil.
B=oNI/L
L is length of coil. N is number of
turns around coil. o = 4 E - 7 N/A2
Magnetic fields come from electric charges moving through space. T
on the last page but now it must move perpendicular to the B field lines. Why? Also
recognize the resulting path is circular rather than parabolic.
Why Does a Charge Curve When Crossing B Field Lines?
Before finishing this lesson this question must be add
R = v t (semicircle)
Examples 19.5 and 19.6 use part of the above equations. Unfortunately, both examples
fail to analyze the time of flight. The equations from the third column can be used.
Example 19.5 would use the first form since the path is a comple
Homework Problems 19: 27, 29, 30, 32.
Lesson 3-24
19.4 and 19.5
Magnetic Forces on Currents
Suppose that an electrical current flows perpendicular to a magnetic field. You can
consider how the magnetic field pushes on the individual charges or you can wri
Opposing Magnetic Force
As the bar is pulled through the magnetic field there will be a noticeable opposing
force. The magnetic field of the induce current will add to the first magnetic field on the
leading edge of the sliding bar. On the trailing edge o
Change field strength.
Change ring area.
Rotate the ring.
1st. To change the field strength you generally increase or decrease current source that is
producing the magnetic field or move the ring closer or farther from field source.
2nd.Shrink or expand t
Study figure 19.29 where two currents are
running parallel. One current creates a
magnetic field that exerts a force on the other
current. The opposite is also true according
to Newtons 3rd Law. As shown in figure 19.29
the magnetic field of I2 exerts a f