Preface: review of terms, notation, and exponents [for example}:
u = 10 -6, m = 10 -3, M = 10 6
The coulomb is the measure of charge, and ONE electron has -1.602 X 10 -19 coulombs of charge.
CHAPTER 1
1. Electrical engineering is a broad field, with numerous subfields: power, electromagnetics, communications, computers, electronics, systems, controls. We touch on many of these fields.
2. An electron has - 1.602 X 10 -19 Coulombs of charge, so one coulomb contains 6.25 X 10 18 electrons. An ampere is the transfer of one coulomb in one second.
3. DC = direct current, which has one value of current flowing in the wire continuously. AC is alternating current, where the current goes back and forth - reversing direction. It is specified by the frequency [cycles per second, called a hertz], which is the inverse of time in seconds. Detroit Edison sells AC current, at a frequency of 60 HZ. Europe’s AC is 50 HZ.
4. Force between TWO charges: F = k [q1 * q2]/d2 , where q1 is the charge in C of charge 1, q2 is the charge in C of charge 2, d is the distance between them in meters, and k is a constant: 8.99 X 10 9 newton-meter 2 / C2
5. You can spot conductors and insulators on the periodic table, and depends on the charge movement allowed by the material. This depends on the number of electrons in the outer shell of electrons. Metals are generally conductors, carbon and the like are insulators, and silicon/germanium fall in between: semiconductors.
6. Current = I = dq/dt, Voltage = dw /dq = the potential energy. W is energy in joules.
7. Since we are talking about charges, we have plus and minus signs. When we have a circuit, we will write the flow of currents, and the drop of voltages and ASSUME a +/- direction. The values of current and voltage may then be either POSITIVE or NEGATIVE, because we just assumed a direction.
8. Power = A Watt = volts X amperes = dw/dt. Power in an element may be absorbed or supplied, depending on the signs [ - means supplied, + means absorbed]. When the element is supplying energy, a positive current enters the negative terminal and leaves via the positive terminal.
9. Three ideal passive circuit elements are the resistor, the capacitor, and the inductor.
V = IR for the resistor , [where R is resistance in ohms]
V = L * di/dt , [where L is inductance in henrys]
I = C * dv/dt [Where C is capacitance in farads]
Homework: Chapter 1 all problems, due Monday, September 8, 2003.
1. 15 A 12 V car battery delivers 200A of current starting up in 1 second. How much energy is supplied?
P = vi = dw/dt = 2400 Watts. W= the integral of p * dt over 0-1 seconds. So w = 2400 joules.
1.1: DC = car battery, solar cell, watch battery
AC = residential power outlet, commercial power generating station
1.3 Edison’s total output: 83 watts X 400 lamps = 33200 watts
1.10 [the point of this exercise is to adjust the value for the signs]:
a. v = - 10 volts, I = 1 amp
b. v = -2 volts, I = 2 amp
c. v = 1 volt, I = - 1 amp
1.6 Two identical forces will repel each other. Unlike forces attract.
F = k [q1 * q2]/d 2 = [: 8.99 X 10 9 newton-meter 2 / C2]*[0.01 uC * 0.01 uC]/0.01m
1.14 One electron volt is the amount of energy gained by an electron moving through a voltage difference of one volt. What is this energy expressed in joules? dw = v * dq = one volt * [- 1.602 X 10 -19 Coulombs]
1.4: Find this on your back page!: infrared = 10 14, shortwave = 10 7. Gamma = 10 22 ; all in HZ.