1. Wiring, Voltage, Current, Charge, Color Code
2. Physics of Electricity and Magnetism
3. Algebra, Geometry, Trigonometry
4. Polar Coordinates
5. Batteries, Series, Parallel DC Circuits, Resistors, Capacitors, Inductors
6. Network Theory and Magnetics
7. AC Circuit Theory
8. Three Phase Circuits
9. Transistors and Amplifiers
10. Circuit Blocks

Electricity is distributed to homes in the United States with a three wire system. Of the wires coming into the home from the street, one wire, connected to ground is called, Neutral, and if it is insulated, the color of its insulation is White. The other two wires are called, Phase or Hot, and their insulation is usually colored red and black. The voltage measured from black to red is 240 volts, and the voltage from either black or red to neutral is 120 volts. The electric service to a home is established by connecting the two Phase wires to a double pole main circuit breaker. The output of this breaker is connected to two bus bars from which branch circuit breakers derive their power. The ground wire is connected to another bus bar, which is called the Ground bus. This usually has a quantity of holes and tightening screws.

A typical 120 volt branch circuit consists of three wires. One of them comes from the branch circuit breaker, and is called by the National Electrical Code (NEC) the "ungrounded conductor". Its insulation is usually black. The other two come from the ground bus. One of them is usually white and is called the "grounded conductor", and is the return path through the load for current to flow. The third one is called the "grounding conductor", and is the safety conductor. It would be connected to the cabinet of a washing machine for example so that any leakage current to the cabinet would be conducted to ground, and not pose a danger to the equipment user. It can be a green wire, the bare wire in non-metallic cable, the armor of BX (armored) cable, or the tube (pipe) of electrical metallic tubing (EMT). Unfortunately the grounding system connections may not be as carefully maintained as those of the other conductors, thus posing a potential problem. More will be said about this later.

The newer receptacles have three openings on their face. Two are parallel and accommodate blades, and the third has a 'U' shaped hole which accommodates a round pin on the plug. This is the connection to the grounding conductor. Of the two blade openings, one is larger than the other. The larger one connects to the grounded conductor, which leaves the smaller one to connect to the ungrounded conductor.

Extension cords, and cords which connect to lamps have one of their blades larger than the other so that they will fit into a receptacle in only one way. The larger one (connected to the grounded conductor) would be connected to the screw shell of a lamp socket. In this way, if one is changing a bulb, with the switch 'on', and touches the screw shell of the bulb, there should be no danger of a shock. However, sometimes errors are made in wiring, and so caution should be the watchword even though the system is designed with safety in mind.

Voltage is a measure of the "Electrical Pressure", or force between any two points. For the purpose of this lesson, these two points will be considered two wires. Its analogy to the concrete physical world would be water pressure. The higher the pressure, the higher the force that is exerted.

Pressure by itself has no value. It only has value when it acts upon something and moves that something. In the water analogy, the something that moves is the water itself. All other things being equal, the higher the pressure, the more water will flow.

In electricity, the "thing" that flows is the current. Even here, the water analogy is evident, as in, "a water current". The current is a physical entity, Electrons, one of the elementary particles of physics. Since an electron is such a small entity, both in size, and in physical properties, current is measured in amperes giving a more manageable quantity to work with. The physical property of an electron that we exploit is its "Charge". Again, since the charge of a single electron is so small, we measure the charge in Coulombs.

One ampere of current is defined as a charge of one coulomb flowing per second. It is as if we had a window through which we could look at electrons flowing in a wire. If the number of electrons that equal one coulomb flows past the window in one second, then the current is one ampere.

Some of the components used in electronic products are so small that printing numbers on the component are impossible or impractical. A color code has been established to solve the problem. It is based on the spectrum with extra colors to provide 10 digits. They are:

0 1 2 3 4 5 6 7 8 9

A mnemonic has been devised to enable us to remember the code. Although it is sexist, it is a great help in remembering.

In a resistor, the colors are applied as bands. The first two bands denote the first two digits. The third band stands for a multiplier, or the number of zeroes following the first two digits. For example, Red, Blue, Yellow denotes a 260,000 ohm resistor. That is, Red = 2, Blue = 6, and Yellow = 4, or 4 zeroes following the first two digits. Additional bands are used to denote other attributes such as, precision (percent tolerance), temperature coefficient, etc.