1. Travis M.

2. Light Emitting Diodes - They do dozens of different jobs and are found in all kinds of devices. Among other things, they form the numbers on Digital clocks, transmit information from remote controls, light up watches and tell you when your appliances are turned on. Collected together, they can form images on a jumbo television screens or illuminate a traffic light. Basically, LEDs are just tiny light bulbs that fit easily into an electrical circuit. But unlike ordinary incandescent bulbs, they don't have a filament that will burn out, and they don't get especially hot. They are illuminated solely by the movement of electrons in a semiconductor material, and they last just as long as a standard transistor.

3. CDS Cells -CdS cells are a type of photoconductive device. They are semiconductor sensors that utilize the photoconductive effect in which light entering the photoconductive surface reduces the resistance. A voltage is applied to both ends of a CdS cell and the change in resistance due to light is output as a current change signal. Despite of small size, the output current per photoconductive surface area is large enough to drive relays directly. For this reason, CdS cells are used in a wide variety of fields.

4. Resistors Resistors, like diodes and relays, are another of the electronic parts that should have a section in the installer's parts bin. They have become a necessity for the mobile electronics installer, whether it be for door locks, braking lights, timing circuits, remote starts, LED's, or just to discharge a stiffening capacitor. Resistors "resist" the flow of electrical current. The higher the value of resistance (measured in ohms) the lower the current will be. Resistors are color coded. To read the color code of a common 4 band 1K ohm resistor with a 5% tolerance, start at the opposite side of the GOLD tolerance band and read from left to right. Write down the corresponding number from the color chart below for the 1st color band (BROWN). To the right of that number, write the corresponding number for the 2nd band (BLACK). Now multiply that number (you should have 10) by the corresponding multiplier number of the 3rd band (RED)(100). Your answer will be 1000 or 1K. It's that easy.

5. So how does the fluctuation make the speaker coil move back and forth? The electromagnet is positioned in a constant magnetic field created by a permanent magnet. These two magnets -- the electromagnet and the permanent magnet -- interact with each other as any two magnets do. The positive end of the electromagnet is attracted to the negative pole of the permanent magnetic field, and the negative pole of the electromagnet is repelled by the permanent magnet's negative pole. When the electromagnet's polar orientation switches, so does the direction of repulsion and attraction. In this way, the alternating current constantly reverses the magnetic forces between the voice coil and the permanent magnet. This pushes the coil back and forth rapidly, like a piston. Speakers

6. Capacitors/ Disc Capacitors In a way, a capacitor is a little like a battery. Although they work in completely different ways, capacitors and batteries both store electrical energy. If you have read How Batteries Work, then you know that a battery has two terminals. Inside the battery, chemical reactions produce electrons on one terminal and absorb electrons on the other terminal. A capacitor is much simpler than a battery, as it can't produce new electrons -- it only stores them. In this article, we'll learn exactly what a capacitor is, what it does and how it's used in electronics. We'll also look at the history of the capacitor and how several people helped shape its progress. Inside the capacitor, the terminals connect to two metal plates separated by a non-conducting substance, or dielectric. You can easily make a capacitor from two pieces of aluminum foil and a piece of paper. It won't be a particularly good capacitor in terms of its storage capacity, but it will work.

7. Rheostat, a device used to regulate an electric current by increasing or decreasing the resistance of the circuit. Some common uses of the rheostat are to dim lights, to control the speed of an electric motor, and to control the volume of a radio. The accompanying diagram shows a simple rheostat. Current flows into the resistance coil and from the resistance coil through the slider. When the control knob is turned, the slider moves along the coil; the amount of resistance is thus changed by varying the length of the current's path through the resistance coil. Rheostats A.K.A- Potentiometers

8. The figure below shows the shape of the magnetic field around the wire. In this figure, imagine that you have cut the wire and are looking at it end-on. The green circle in the figure is the cross-section of the wire itself. A circular magnetic field develops around the wire, as shown by the circular lines in the illustration below. The field weakens as you move away from the wire (so the lines are farther apart as they get farther from the wire). You can see that the field is perpendicular to the wire and that the field's direction depends on which direction the current is flowing in the wire. The compass needle aligns itself with this field (perpendicular to the wire). Using the contraption you created in the previous section, if you flip the battery around and repeat the experiment, you will see that the compass needle aligns itself in the opposite direction. Electromagnetic Coil

9. Direct Current Motors Let's start by looking at the overall plan of a simple two-pole DC electric motor. A simple motor has six parts, as shown in the diagram below: Brushes Axle Field magnet DC power supply of some sort An el­ectric motor is all about magnets and magnetism: A motor uses magnets to create motion. If you have ever played with magnets you know about the fundamental law of all magnets: Opposites attract and likes repel. So if you have two bar magnets with their ends marked "north" and "south," then the north end of one magnet will attract the south end of the other. On the other hand, the north end of one magnet will repel the north end of the other (and similarly, south will repel south). Inside an electric motor, these attracting and repelling forces create rotational motion. ­