What is Electricity?
 
So what is electricity and where does it come from? More importantly, why is carpet, socks and a doorknob a bad combination? In its simplest terms, electricity is the movement of charge, which is considered by convention to be, from positive to negative. No matter how the charge is created, chemically (like in batteries) or physically (friction from socks and carpet), the movement of the discharge is electricity.


Understanding Current

This flow of electrical charge is referred to as electric current. There are two types of current, direct current (DC) and alternating current (AC). DC is current that flows in one direction with a constant voltage polarity while AC is current that changes direction periodically along with its voltage polarity. Thomas Edison and Alessandro Volta were pioneers in DC current and wrote much of electricity’s history. But as societies grew the use of DC over long transmission distances became too inefficient. Nikola Tesla changed all that with the invention of alternating current electrical systems. With AC it is possible to produce the high voltages needed for long transmissions. Therefore today, most portable devices use DC power while power plants produce AC


Ohms Law

The most fundamental law in electricity is Ohm’s law or V=IR. The V is for voltage, which means the potential difference between two charges. In other words, it is a measurement of the work required to move a unit charge between two points. When we see a value such as 10 Volts, it is a measurement of the potential difference between two reference points. Normally the two points will be +10V and 0V (also known as ground), but it can also be the difference between +5V and -5V, +20V and +10V, etc. In the field, you might hear the term “common grounds” which refers to each device in a system using the same zero-point reference (or ground) to ensure the same potential difference ( or voltage) is applied throughout the system. The next component of Ohm’s law is current, the units of which are Amperes; in the formula, current is represented by the very logical choice of the letter I. As mentioned previously, current is the measurement of the flow of charge in a circuit. This leaves us with the letter R which represents Resistance. Electrical resistance, measured in Ohms, is the measure of the amount of current repulsion in a circuit. Simply, resistance resists current flow. When electrons flow against the opposition offered by resistance in the circuit, friction occurs and heat is produced. The most common application for resistance in a circuit is the light bulb. The light bulb introduces enough resistance in a circuit to heat up the filament inside, causing light to be emitted. Resistance in a circuit can also be helpful when needing to alter voltage levels, current paths, etc. Resistors are self-contained packages of resistance that can be added to a circuit and are commonly used to divide voltage levels.