Electricity Terms and Understanding
The Coulumb
The coulumb measures the quantity of electrons. One coulumb contains 6.25x10^18 electrons. The coulumb is a quantity measurement just like litres or gallons. To get a grasp of just how many electrons are in a coulumb try comparing 1 second to 200 billion years. The coujlumb comes from the 1700's French scientist Charles Augustin De Coulumb.
The Ampere
The ampere is named after the 1700's scientist Andre Ampere, most famous for electromagnetism. The ampere (amp) is equal to 1 coulumb per second. The ampere measures the amount of electricity flowing through a circuit. The amp is commonly represented in formulas as the letter I.
The Watt
The watt is the measurement of the amount power being used in a circuit. The watt was named after an English scientist James Watt. The letter P is generally used to represent watts in a formula.
The Volt
Voltage is also called potential difference or electromotive force (EMF). It is the force that pushes electrons through a wire inducing current and can be looked at as electric pressure. 1 volt is the amount of potential to cause 1 coulumb to produce 1 joule of work. Volts in formulas are commonly represented as V or E.
The Ohm
The ohm is used to measure resistance of current flow. An ohm is the amount of resistance that allows 1 ampere of current to flow when 1 volt is applied. All electric loads such as: lamps, motors, heating elements etc, are all forms of resistance measured in ohms. Ohms in formulas are commonly represented as R.
Basic Electric Overview
Anyone who works in the electrical field learns and understands the basic units used to measure electric power.
Before current can flow through a circuit, a complete path must exist. A complete circuit is often referred to as a closed circuit, because a power source, conductors, and load form a closed loop.
A short circuit is another type of circuit, which has little or no resistance. This generally occurs when the conductors leading from and back to the power source become connected.
One more type of circuit is a grounded circuit, often confused with a short circuit. Grounded circuits can cause an excessive amount of current flow. This happens when a path other than the intended on is created to the ground. Many circuits often contain an extra conductor called the grounding conductor. The grounded conductor also called neutral; provides the return path and completes the circuit back to the power source. A grounded conductor generally connects to the case of an appliance providing a low resistance path to the ground.
Ohm's Law
Put simply, Ohm's law says that it takes 1 volt to push 1 ampere through 1ohm. Ohm discovered that electric quantities are proportional to each other and can be expressed as math formulas. He found that if the resistance in a circuit stayed the same and the voltage went up, the current would increase as well. Reversely, if the voltage dropped the current decreased while the resistance remained constant. He also found that if the voltage stayed constant and the resistance went up, the current would then decrease.
That being said, since Ohm's Law is a statement of proportion, it can be made into an algebraic formula when the volt, the amp, and the ohm are used.
The three basic Ohm's Law formula are:
E= I x R
I= E / R
R= E / I
Where E= EMF or voltage, I= current or amperage, and
R= resistance. The chart above can also act as guide when using Ohm's Law.
OR
Flow Theory
The Electron Flow Theory
The electron flow theory states: since electrons are negative, current flows from the most negative point in a circuit to the most positive. The electron flow theory is most widely accepted as the correct theory and is most commonly used in electrical calculations.
The Conventional Current Flow Theory
A secondary and older theory, the conventional current flow theory states that current flows from the most positive point to the most negative. Although the electron flow theory has be shown to be the most correct, the conventional current flow theory is still widely used for several reasons. A lot of electronic circuits use the negative terminal as ground or common. If the negative terminal is used as ground then the positive is considered above ground. Many people in the electronics industry still use this theory because the arrows on semi conductors point in the direction of conventional current flow.