Physics

How Electrical Current Flows



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Although it is not advisable to mix water with electricity, we can understand electrical current flow if we compare its behavior to that of water. There are many similar behaviors to observe.

Flashover and sideflash is equivalent to a flood.

Balance, equilibrium, or "reference" voltage is equivalent to a stabilized water level, as in pooling.

Arcing is equivalent to splashing.

An electrical circuit is equivalent to a pathway for water, as in a stormwater drainage system, creek, or riverbed.

A complete electrical circuit is equivalent to a flow of water.

The movement of electrically charged particles (plus or minus) characterizes an electrical current. The charged particles are either electrons (charged minus) or ions (charged either plus or minus).

Metallic conduction describes the flows of electricity that are widely controlled within a facility. It is characterized by electrons moving through a metal conductor with no obvious chemical changes or movement of atoms in the metal. Where there are sufficient conductors to support current flow, there should be no signs of stress or breakdown in them.

A simple, but detailed description of how current flows is given by Sol Medoff and John C. Powers in their book The Student Chemist Explores Atoms and Molecules*:

"The last type of bond in our discussion is the "metal" bond. Metals always have one or more empty orbitals. This means that the valence electrons can jump. They can jump all over the place. Atoms of metals are arranged next to each other. The jumping electrons visit other atoms. In fact, they can no longer be identified with the original atom they came from. They go very fast, through the entire metal system of atoms. The atoms, minus their moving electrons, become charged plus. The metal bond now becomes plain. The sea of moving electrons are, at the same time, held by attraction to the plus atoms. Thus, they are like billions of cords held tightly to the package. The metal bond is a powerful one.

"The moving electrons give the metal some of its characteristics. The electrons move in waves that capture light waves. All of the light waves (or almost all) are then radiated back. The metal assumes a high luster. If one end of the metal is heated, the electrons move even faster. The entire metal object is affected, and the whole thing becomes 'hot.'

"In the case of electricity, an additional load of electrons are fed into the metal. The additionals are past the neutral point. No more electrons are needed by the metal. Either the new electrons move through empty orbitals, or they push other electrons down the metal by repulsion. In any case, the metal bond causes the metal to allow a flow of electricity."

Another form of conduction is ionic or electrolytic conduction, characterized by a motion of ions through a liquid. This process is associated with electrical generators and storage batteries. A battery uses the energy from an oxidation-reduction reaction to produce an electric current flow. An electrochemical battery or galvanic cell is a device powered by an oxidation-reduction reaction where the oxidizing agent is separated from the reducing agent so that the electrons must travel through a wire from the reducing agent to the oxidizing agent.

Geomagnetism and Current Flow

Geomagnetism induces some current flow that creates differences in voltage (also called "potential") between specific points on the Earth. This current flow is the safest known to occupants because it occurs outside the facility and underground.

The Grounding Electrode System (GES) shares this current with the facility on a real-time basis (at speeds of 0.7c to 1c) via the Grounding Electrode Conductor (GEC) which ends at the ESE and bonds to the main bonding jumper. This jumper transfers the current to the grounding wires and isolated neutral at the supply side of the Electrical Power Service Entrance (ESE). The isolated neutral and grounding wires called equipment grounding conductors carry this current further into the facility from the load side of the ESE.

When equipment grounding conductors and the main bonding jumper are connected to the ESE enclosure, the whole enclosure becomes a conductor with a lot of surface, or cross-sectional, area for handling current flow across it.

Any sub-panels are located downstream from the ESE, and their function is to further divide circuits for distribution indoors. The current from the ground is passed along downstream through the electrical conduit system and all sub-panels to junction boxes and to device boxes such as power outlets, lighting fixtures, and switches. Ground current will pool evenly across all these points. This balanced current is an indicator of current electrical copies.

Manmade Current Flow

Electrical transmission and distribution begins at a power plant which first produces electricitiy. The plant then sends the electrical power over a grid of wires that ends at consuming facilities. In the United States, electrical power is transmitted at a frequency of 60 hertz as alternating current. This AC is transmitted in one direction only down isolated wires that permit stacking of additional current on the grid.

Alternating current is sometimes believed to travel in "two directions" or "forward and reverse" across the supply and return wires. In fact, it is transmitted across the supply conductors only in a single direction. Once consumed, the electricity continues the single direction path across neutral / return wires. The entire path resembles a circular loop, but the direction of travel is still one-way, and ultimately "round trip."

Current that returns to a power utility from consumer facilities will parallel neutral return wire pathways. Neutral and return wires are commonly grounded at overhead utility poles, as well as in underground configurations, so returning current commonly flows in a parallel fashion along return wires and through the ground back to a utility.

Summary

Electrons are charged minus and repel each other, causing a pooling of electrons at all available plus environments.

Electrical current jumping across two points having different voltages is flashover.

Metallic conduction is typically associated with our control of current flow in a facility, and works well when there are plenty of conductors to handle the current.

Balanced and ample current flow figures prominently in a strong grounding cone of protection and current electrical copies.

*Medoff, Sol. The Student Chemist Explores Atoms and Molecules. New York: Richards Rosen Press, Inc., 1977.

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