LUIGI GALVANI (1737- 98) ALESSANDRO VOLTA (1745-1827)

1791 & 1799 – Italy

‘Galvani: An electric current is produced when an animal tissue comes into contact with two different metals.

Volta: An electric current is not dependent on an animal tissue and can be produced by chemicals’

Galvani was wrong and Volta was right.

Galvani had found that by touching a dead frog’s legs with two different metal implements, the muscles in the frog’s legs would twitch. Galvani wrongly concluded it was the animal tissue that was storing the electricity, releasing it when touched by the metals. He felt he had discovered the very force of life – ‘animal electricity’ – that animated flesh and bone.

portrait of LUIGI GALVANI ©

GALVANI

Soon dozens of scientists were trying to bring corpses back to life by electrifying them. Volta was not convinced the animal muscle was the important factor in the production of the current.

He repeated Galvani’s experiments and concluded, controversially at the time, the different metals were the important factor.

A bitter dispute arose as to whose interpretation was correct. Volta began putting together different combinations of metals to see if they produced any current; later he produced a wet battery of fluid and metals. Volta’s method of producing electric current involved using discs of silver and zinc dipped in a bowl of salt solution. He reasoned that a much larger charge could be produced by stacking several discs separated by cards soaked in salt water – by attaching copper wires to each end of the ‘pile’ he successfully obtained a steady current.

The ‘voltaic pile’ was the first battery in history (1800). Napoleon Bonaparte, who at the time controlled the territory in which Volta lived, was so impressed he made him a Count and awarded him the Legion d’Honour.

portrait of ALESSANDRO VOLTA ©

VOLTA

Volt, the SI unit of electric potential, honours Volta.

Although Galvani’s theory on ‘animal electricity’ was not of any major importance, he has also achieved nominal immortality; like ‘volt’, the words ‘galvanic’ (sudden and dramatic), ‘galvanised’ (iron or steel coated with zinc) and ‘galvanometer’ (an instrument for detecting small currents) have become part of everyday language.

A volt is defined as the potential difference between two points on a conductor carrying one ampere current when the power dissipated between the points is one watt.

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CHARLES DE COULOMB (1736-1806)

1785 – France

‘The force of attraction or repulsion between two charges is directly proportional to the product of the two charges and inversely proportional to the square of the distance between them’

The region around a charged object where it exerts a force is called its electric field. Another charged object placed in this field will have a force exerted on it. Coulomb’s rule is used to calculate this force.

Coulomb, a French physicist, made a detailed study of electrical attractions and repulsions between various charged bodies and concluded that electrical forces follow the same type of law as gravitation. Coulomb found a similar principle linking the relationship of magnetic forces. He believed electricity and magnetism, however, to be two separate ‘fluids’.
It was left to HANS CHRISTIAN OERSTED, ANDRE-MARIE AMPERE and MICHAEL FARADAY to enunciate the phenomenon of electromagnetism.

The SI unit of electric charge, coulomb (C), one unit of which is shifted when a current of one ampere flows for one second, is named in his honour.

He also articulated Coulomb’s rule of friction, which outlines a proportional relationship between friction and pressure.

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HANS CHRISTIAN OERSTED (1777-1851)

1820 – Denmark

‘Electric current produces a magnetic field’

drawn portrait of HANS CHRISTIAN OERSTED ©

Oersted discovered that an electric current could make the needle of a magnetic compass swivel. It was the first indication of a link between these two natural forces. Although Oersted discovered electromagnetism he did little about it. This task was left to AMPERE and FARADAY.

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