Unit of Measure for Resistance

Electricity has been around for a long time, in one form or another. In the late 18th century, Italian physician and physicist Luigi Galvani discovered that by introducing small static electric impulses to a dissected frog's leg, it would twitch. That was a very important discovery, which in turn would lead to many others, which ultimately brought us today's modern microprocessors, containing and working together with many other components embedded in integrated circuits.

Electrical resistance

A regular copper wire has a built-in resistance which, when strung over a distance, is measured as line loss.

At the same time, the filament in tungsten-style incandescent light bulbs acts as a resistor. This characteristic manifests itself by creating light when the two wires are led to the filament in a vacuum.

The entire process is known as Ohm's Law, which has three components.

Ohm's Law

In its basic formula, you have three qualities that are necessary to describe a functioning electrical circuit:

  1. I, which represents the current in amperes
  2. V, being the voltage powering the circuit
  3. R, the resistance

By having two of the three figures, the third one is always obtainable by applying Ohm's Law, which states that I = V / R. Inversely you can also determine the values of V and R: V = I x R and R = V / I.

Resistors have been used in electrical applications since their beginnings, and, with the miniaturization of electronics, they have taken on a whole new importance when operating in conjunction with the large number of transistors found on integrated circuits. To know the resistance of a particular device, for larger applications a multi-meter is very practical. It gives you volts AC and volts DC, as well as impedance, also known as resistance in ohms.

Resistor color code

If you are able to physically access the resistor itself, there is a second method of calculating its resistance, a very handy color code that will tell you what the given properties of a resistor are.

The discoverer of the principles behind Ohms Law

He was none other than Herr Georg Simon Ohm, born in Bavaria in 1789 during an age of great physics discoveries. His father, a self-taught craftsman, took great pride in educating his children, bringing them up in a very secure intellectual environment and teaching them mathematics, philosophy, chemistry and physics. Georg, at the tender age of 17, became a mathematics teacher in Switzerland, where he continued his studies at the same time, receiving a doctorate in mathematics in 1811 at age 22. Upon reaching that milestone, he joined the university staff as a lecturer.

From there, he joined the Jesuit Gymnasium in Cologne, as it had a reputation as having one of the best-equipped laboratories in Europe. By the early 1820s, he had started his own experimental work in the new field of electromagnetism there.

By this time he had already concluded that the mathematical relationship between current, voltage and resistance was an unalterable physical law like gravity.

His first paper dealt with the resistance encountered by current traveling through a wire: the bigger the wire, the less the resistance. By 1826 and 1827 he had laid the groundwork for what would eventually be called Ohm's Law in his book Die Galvanische Kette, mathematisch bearbeitet (.pdf), wherein he mathematically explains the theory of electricity.

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