The course starts with an introduction to the
basic concepts of electric charge and electric field.
Just as the gravitational field makes it easy to calculate the
force on a mass placed in the field (F = mg), knowing value of
the electric field, caused by electric charges, makes it easy
to calculate the force on a charge placed in an electric field
(F = qE).
The concept of force between electric charges,
positive and negative, is studied. Calculations involve the addition
and subtraction of vector quantities. Vector addition, subtraction,
and multiplication (dot product and cross product) will be used
EXTENSIVELY during the rest of the semester. Students have learned
these topics in Mechanics (Physics 50/70) but should review /
learn them now before we start to use them. Forces between charges
give rise to the movement of the charges and hence electric currents.
Calculating the electric field caused by
one or two electric charges is fairly simple, but calculation
of the field caused by a distribution of many electric charges
is more complicated and will require the use of integral calculus
(Math 31 is a prerequisite for this course). Using Gauss' Law
makes the integrals really simple and the calculation easy. Also,
one can calculate the field by first calculating the electrical
potential, a scalar quantity related to the potential energy -
a concept learned in Mechanics (Physics 50/70). As an application
of electric fields, soot particles are removed from industrial
smoke stacks by having electric fields in the stacks that exert
horizontal forces on the electrically charged soot particles.
And electrons moving inside a TV or computer monitor toward the
screen are deflected horizontally and vertically to form images
in the phosphor coating on the screen interior.
Then basic electrical circuits are covered
where students gain a working knowledge of the concepts of electric
charge, electric current, and voltage - topics covered in the
early lab exercises. Simple calculations regarding the relationship
among voltage, current, and electrical resistance in circuits
are learned. Elementary circuit analysis techniques are studied
to determine power dissipated in electrical resistors in more
complex circuits.
The magnetic field, another vector quantity,
is caused by electric charges that are moving with a velocity,
either in an electric current or in space, like the charged cosmic
particles that arrive on Earth from the Sun. Calculation of the
magnetic field in this course generally involves integral calculus,
but the integrals in Ampere's Law are simple and tabulated. Magnetic
fields are essential for the operation of electric motors and
computer memory.
Voltages can be induced, or generated, in a wire
loop by varying the magnetic fields near them. These generated
voltages produce electromotive forces and induced, or generated,
electrical currents. Faraday's Law governs the generators used
by power plants to produce electricity so important in our modern
technological lifestyle.
With a knowledge of electric and magnetic fields
and the energy associated with them we can understand and analyze
how alternating current (AC) circuits work. These circuits
provide the high frequencies necessary to operate our cell phones,
TV stations, and other communications systems.
The course ends with a discussion of Maxwell's
equations, most of which we will already have used in the
course. These equations provide the basis for all of electromagnetic
theory and predict the propagation of the electromagnetic waves
(radio, TV, microwave, x-rays, light) used in our communications
systems and optical devices and systems.