Electricity is a form of energy that comes from the movement of electrons from one atom to another. When enough electrons are in motion, they can do things like create heat or generate magnetic fields that power motors. Many things, from computers to refrigerators, heating and air conditioning systems, light bulbs, televisions, phones and even cars, rely on electricity in order to function. Without electricity, few modern comforts and technologies would be possible, and learning about how electricity works can help people to better appreciate the conveniences that this resource affords the world, today.
Electric Potential Difference
The concept of electrical potential difference refers to the imbalance in the number of electrons in one area versus another. For instance, when a person walks across a carpet they may acquire a lot of excess electrons that attach themselves to their body. These electrons are excess because they outnumber the protons that exist within the atoms of the object, in this case a person's body. When they touch a metal object, such as a door knob, the object they touch has no excess electrons. The electrons from the person's body will rush into the door knob in what's called an electric current, causing an electric discharge, which results in a painful shock. The magnitude of the discharge is proportional to the electric potential difference. Another word for the term "electrical potential difference" is voltage.
When groups of electrons move in one direction from one area to another, it is called an electric current. All electric power depends on the existence of an electric current. The current that powers a typical light a bulb will have trillions of electrons moving in the same direction. Individual electrons move slowly, but when trillions are moving at the same time, they can accelerate to nearly the speed of light. This is because large numbers of electrons move much like a dozen pool balls lined up in a row. As soon as the one in the rear pushes forward, the others move forward slowly, but the ball in the front moves rapidly. For a current to exist there must be a conductor, or a material through which electrons can flow, and there must be a difference in electric potential, or a difference in voltage. Conductors can be wires or other metallic objects; however, electrons can also flow through the air under certain conditions as well. One example of electricity flowing through air is the weather phenomenon referred to as lightning. When electrons flow through a current and return to their source, such as a battery, it is called a closed loop, or a circuit. The term for measuring an electric current is called the ampere. One ampere, or amp, represents 6.241 x 10E18 electrons moving in a current. The coulomb is a term for measuring the amount of electrical current moving per second. One coulomb means one ampere per second.
Similar to the flow of water through pipes, electrons may face obstructions to the flow of an electrical current. These obstructions are known as electrical resistance. Some materials, such as copper, have less resistance than others, such as the filament in a light bulb. When electrons run into materials that create resistance, electrical energy will be lost and the resistant materials will heat up in a process called Joule heating. This process is often put to use in things like heating irons or stoves. Superconductors are materials that offer zero electrical resistance and as a result no loss of electrical energy. All other types of materials have some level of resistance. The scientific unit of measurement that pertains to resistance is called the ohm.
There are two major types of electric circuit connections; a series circuit and a parallel circuit. A series circuit connection is when there is exactly one path for electrons to flow in an electric current. If the circuit has a battery and three lights, electricity will flow in a sequential path from the battery to the first light, the second light, and then the third light, and finally back to the battery. Each light creates additional resistance, which reduces the amount of electricity available to the next one, meaning the third light may be dimmer than the first. If the path is broken in any way, then there is no electric current, which means one or more lights will not receive electricity and will go dark. This is similar to water flowing through a single pipe from one end to another. If there is a blockage then the flow of water will stop and fail to reach the other end.
In a parallel circuit connection, electrons flow through two or more paths. This means that the electric current will flow from the battery, and then split up into three paths to flow through each of the three lights at the same time, before converging to flow back to the battery. In this type of connection, one of the three pathways can be removed and the other two will continue to receive electricity and stay lit. This is similar to water flowing through a pipe that splits into three pipes. If one of the three pipes is blocked then water will simply flow through the other two to reach its destination. In addition, each light receives an equal amount of electricity, which means one light won't be dimmer than the other. A combination or complex circuit connection is a circuit connection which utilizes a combination of parallel and series connections. In this type of circuit connection, there will be some pathways that are purely linear and others that are parallel in nature.