Carros

Basic Electrical Principles
IT'S ELECTRIC!!
Electricity. It's everywhere. It's in your house, in the computer on which you are reading this, in the air, in your body, blah blah blah. You get the point. It also plays an important integral part of sound systems. From the microphone to the loudspeaker, everything is electrical, and you need to know a few things about it.
ANYONE FOR FROGS' LEGS?An Italian scientist named Alessandro Volta did experiments with electric charge back in the 1800s; he managed to make dead frogs (yes, frogs) "move" by using them as part of an electrical circuit, and is credited with providing us with a lot of information about electric potential. The volt was thus born. Voltage is defined as the electric charge between two points. In household terms, voltage isakin to water pressure available to do work. It can't do any work until a circuit (the plumbing and a water tap) is complete so that current (the amount of water) can flow. In engineering terms, voltage is the potential energy of a bunch of electrons. Current, measured in Amperes, is the flow of electric charge; we can say that current is the rate of flow of electrons, but technically it is theopposite flow that we call current-- as electrons move in one direction, holes are left behind, and appear to flow in the opposite direction. We should also remember from our physics classes that there is a fundamental equation used in electricity: Ohm's Law.
OHM SWEET OHM
Ohm's Law is the mathematical relationship between voltage, current and resistance. It is named after George Ohm, itsfounder. Ohm's Law states that the current in a conductor is directly proportional to the voltage across it, and inversely proprtional to its resistance. In simpler terms, the law states that more voltage will produce more current if resistance stays the same, but higher resistance will cause the current to decrease if the voltage stays the same. In our household plumbing example, we can say that Ohm'sLaw dictates that more water pressure will produce more output if the diameter of the pipe stays the same, but a smaller-diameter pipe will cause the output to decrease if the water pressure stays the same.
With these three basic components, we have electricity. Current is "drawn" from a power supply due to the presence of a voltage placed across a load, or resistance. For instance, a typicalelectrical outlet has 120 volt potential (pressure- it has the capacity to give you 120 volts), but nothing is connected. If you put some load across its terminals, like a lightbulb or steam iron, you then have a complete circuit in which electrical current can flow. As we said before, a higher resistance will yield less current than low resistance. A direct short will cause a very large flow ofcurrent, because there is no resistance. If the supply is capable of delivering enough current, it is likely that the wire will eventually heat up and melt. This is why circuit-breakers and fuses are used. They limit current flow by opening (as opposed to shorting) a circuit before current flow becomes too large-- a 15A circuit-breaker will trip when the loads connected to that circuit try to pull morethan 15A of current.
Makes sense, right? Good. Ohm's Law is represented as the rate of flow of electrons, and voltage is represented as the electric charge between two points.
• Ohm's Law:V = I x R, where V = Voltage, I = Current, and R = Resistance.
HELL'S BELLS
Electricity appears in two forms: alternating current (AC) and direct current (DC). Direct current does not change directions--the electron flow is always from the negative pole to the positive pole-- although as we mentioned before, the electrons themselves don't really "move," it's the holes that are created that "move." Direct current is almost always what is used inside of electronic devices to power the various internal components, but it is a harmful thing in audio signals, which are alternating current....