**Ohm—the ‘Om’ of electricity – George Simon**

**Ohm**

Ohm, George Simon (1789 to 1854) German physicist was born in Bavaria, son of a locksmith and gunsmith. In 1811 he received his doctorate in mathematics.

At the age of 30 Scientist George Simon Ohm joined the Jesuit College at Cologne as professor of mathematics, but his contribution to electrical science was not recognized.

In 1827 Scientist George Simon Ohm contributed Ohm’s Law which states that the current flow through a conductor is directly proportional to the potential difference, i.e., voltage, and inversely proportional to the resistance. I = V/R

V = IR for both alternating (AC) and direct (DC) currents

V(volts) I(amperes) R(resistance in ohms) amperes = volts/ohms. E

I = E / R electric current (I) in a circuit will increase as the electromotive force (E) increases and will decrease as the resistance (R) increases.

Figurative comment : This is almost true in every day life -the more difficult a job is to do, the greater the effort we have to exert to overcome the resistance, in order to get it done.

When a steady current of 1 ampere flowing through a conductor produces a potential difference of 1 volt, the resistance of the conductor is 1 ohm.

In 1833 Scientist George Simon Ohm joined the Polytechnic School, Nuremberg as a teacher. In recognition of his work, Royal Society of London awarded a gold medal in 1843.

For most of his life, Ohm had a meagre living, poorly paid jobs. In 1852, however, he was catapulted to occupy the chair of physics at the University of Munich. He died in 1854.

In 1881, at the meeting of the International Congress of Electrical Engineers at Paris, it was decided that the physical unit measuring electrical resistance was to be named as ‘Ohm’, an immortal achievement of the crowning glory, though posthumous, of course, for George Simon Ohm.

**Ohmmeter ****:** an instrument for measuring electrical resistance which is recorded in ohms.

The unit of conductance is mho (reverse of ohm); now siemen.

**Scientist George Simon Ohm Evolution of ohm**

1827 : 1 ohm = 1 volt/1 ampere.

1893: expressed as the resistance of a standard column of mercury. (Ref: Encyclopedia Microsoft Book shelf ’95)

1948: absolute ohm defined in terms of the wave impedance in a vacuum.

amperes (I) = volts(V)/ohms(R)

**An observation — No match for glorious past**

The three fundamental units of electricity, the ampere, the volt, and ohm are named after an international trio of scientists – Ampere, a Frenchman; Volta, an Italian and Ohm, a German; – a credit to Europe! Europe gave us light in the night, might in the machine and cool comfort.

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