Ohm's Law

History of Ohm's Law

Georg Ohm

Georg Simon Ohm, born on March 16, 1789, in Erlangen, Germany, was a renowned physicist and mathematician known for his groundbreaking contributions to the understanding of electrical circuits. His work laid the foundation for Ohm's Law, one of the fundamental principles in electrical engineering. Ohm began his career as a schoolteacher, but his passion for science and mathematics led him to pursue further studies in physics and mathematics. In the early 1820s, he conducted extensive experiments on the behavior of electricity and developed a deep understanding of electrical circuits.

In 1827, Ohm published his seminal work, "Die galvanische Kette, mathematisch bearbeitet" ("The Galvanic Circuit Investigated Mathematically"), in which he introduced Ohm's Law. This law states that the electric current flowing through a conductor is directly proportional to the voltage applied across it and inversely proportional to the resistance of the conductor. Initially, Ohm's Law faced resistance and skepticism from the scientific community. However, his work gained recognition and acceptance over time, as it provided a quantitative relationship between current, voltage, and resistance, allowing engineers and scientists to analyze and design electrical circuits with precision.

Ohm's Law paved the way for significant advancements in electrical engineering and served as a cornerstone for the development of various electrical applications. It provided a basis for understanding the behavior of electrical circuits, designing efficient power systems, and developing practical electrical devices. Ohm's contributions were eventually recognized and appreciated, and he received several honors and awards during his lifetime. Today, the unit of electrical resistance, the ohm (Ω), is named after him as a tribute to his groundbreaking work.

In other words, voltage measured from a circuit is directly proportional to its current and resistance of the conductors. 

We call this discovery Ohm's Law. For his discovery, we named this value after him. The name of electrical resistance is an Ohm and annotated with the Greek letter Omega (Ω.)

Looking at the animation below we can see that if voltage stays the same the current will change as we increase or decrease resistance- in this case the valve.

The Ohm's Law Formula

Ohm's Law states that at a constant temperature, the electrical current flowing through a fixed linear resistance is directly proportional to the voltage applied across it, and also inversely proportional to the resistance. This arrives at the usual mathematical equation that describes this relationship:

V = IR 1V = 1I(1R)


The Variables

Calculating Ohm's Law

Calculating Ohm's Law is easy algebra. With only three variables the relationship is direct and proportional across the equal sign. By knowing any two values of the Voltage, Current, or Resistance quantities we can use Ohms Law to find the third missing value.


As Voltage changes and Resistance stays the same this means that the Current has to change proportionally. 


As Resistance changes and Voltage stays the same this means that the Current has to change proportionally. 


If you can remember the Ohm's Law Triangle and draw it on a piece of paper, the rest is easy. Covering the unknown in the Ohm's law triangle gives the formula in terms of the remaining variables. If you cover the V, then the remaining variables are I next to R, so V=IR. If you cover the I, the remaining variables are V over R, so I=V/R. If you cover the R, the remaining variables are V over I, so R=V/I.

Ohm's Law is generally applied only to direct current circuits, not alternating current circuits because the current is constantly changing. In DC circuits, other factors such as capacitance and inductance must be taken into account.