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Electrical resistance impedes the flow of electric current and is measured in ohms. Resistance is affected by material structure, geometric composition, insulation quality, impedance, and density. There are two types of resistance: direct current (DC) and alternating current (AC). Excessive resistance creates heat and can be dangerous.
Electrical resistance is a force or material that prevents or resists the free flow of electric current. Since its discovery by George Ohm in the 19th century, it has been measured in ohms.
Electricity is basically a flow of electrons. In the case of electric current, the atoms in the structure of a conductive material allow or prevent the flow of electrons. Poor conductivity means that the atoms are arranged to impede or resist this flow.
The actual measurement of electrical resistance (R) is made by dividing the voltage (V) by the current flow through an object (I), which is expressed in Siemens: R = V/I. The resistance factor is expressed in amperes (amperes).
The resistance of an object or material – its electrical conductance – is based on both its material structure and its geometric composition. Electric current is resisted or enabled based on a number of factors, including the quality of the insulation, the impedance or easement of the conductor, and the density of the object through which the current flows.
There are two basic types of electrical resistance: direct current (DC) resistance and alternating current (AC) resistance. Direct current is the flow of an electric charge or current in only one direction. Alternating current is a back and forth movement of current.
DC resistance is this unidirectional movement of electric current as it encounters the impediment or resistance of its conductor. Using the flow of water through a garden hose, the water would be the current, the water pressure would be the voltage, and the hose would be the conductor. The pipe (conductor) allows unidirectional flow of water (current) within the walls of the pipe. The wall provides a measure of friction (resistance), degrading the force of the water flow. In the case of an electric current, insulating material, imperfections and faults in the electrical conductor create the resistance that the current must overcome.
AC resistance is basically the same as DC resistance, except that resistance is encountered in a multi-directional, back-and-forth current flow. To use the hose example again, one could imagine that the water in the garden hose flows from and then back to the faucet. The friction (resistance) is then multiplied by two.
As mechanical friction creates heat, so does electrical resistance. Just as excessive heat degrades mechanical performance, so it does with electrical performance. Both friction and resistance are, in excess, dangerous and destructive.
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