A megaohm is a unit of electrical impedance, representing one million ohms. Ohm’s law relates voltage, current, and resistance, and was discovered by Georg Simon Ohm in 1827. The ohm is the most widely accepted unit of electrical impedance, and a megohm test is used to check insulation resistance.
A megaohm is a unit of measurement that describes electrical impedance. Meg- is a slightly abbreviated prefix for mega, which is 1×106; -ohm is the basic unit, which is represented by the Greek letter omega (Ω). A megaohm, therefore, is a measure of impedance that represents one million ohms. One ohm relates the resistance of a system to the passage of one ampere of current between two points in a conducting medium, such as copper wire, which is held at a constant potential of one volt. This is the basis of Ohm’s law, named after the German physicist Georg Simon Ohm who first developed this relationship between the most basic elements of electricity in 1827.
The ohm is the most widely accepted unit of electrical impedance in the International System of Units (SI). Electrical impedance is also commonly referred to as resistance, although in reality it is only applicable in the case of direct current (DC). Ohm’s law can be represented by the equation V = IR — V equals voltage measured in volts, I equals current measured in amperes, and R equals the resistance of the conductor.
When Ohm developed what would later be known as Ohm’s law, he was mocked by colleagues and dismissed in ridicule. It would take six years to get his discovery recognized, even though he had shown that the amount of current flowing through an object was directly proportional to the voltage across the material at a fixed temperature. This empirical observation made by Ohm in 1827 provided the basis for understanding electrical circuits.
The unit of proportionality in the relationship between voltage and current is what now bears the name of Ohm. In highly resistive circuits, the ohm is often substituted for the megaohm when single ohms are not an applicable scale. As a result, a megohm test is often used to find out the condition of a system’s insulation, also called an insulation resistance test, where the goal is to maintain a highly resistive path, such as in a refrigeration compressor.
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