SCIENCE
Stelios Mores
Resistance is Futile
I
t was not until the mathematical studies by the English physicist William Gilbert during the mid1600s that a nascent understanding of electricity began to form with his proposal of the existence of an electric fluid comprised of some kind of particles. As his work was based on the electrostatic effects of amber and the magnetic effects of loadstones, he coined the term electricity to describe this ‘fluid’ based on the Greek term for amber (electron). He determined that electricity flowed to the extremities of objects leading to the concept of an electric current and showed that electricity and magnetism were distinctly different phenomena.
The existence of a relationship between electricity and magnetism was first discovered in 1820 by the Danish physicist and chemist Hans Orsted when he noted the effect which an electric current had on a compass needle. This led to the work of the English scientist Michael Faraday, who over the next three decades turned this discovery into a science. In 1831 he showed how magnetic flux crossing a conductor such as a coil could generate an electric current and invented the first electricity generator. Faraday’s discoveries form the basis of all electric motors and conventional electricity generators to this day. Around the same time, a German physicist and mathematician George Ohm began his work on electrical resistance, a phenomenon which results in heat being generated whenever an electric current flows through a conductor. This is the principle upon which the incandescent lightbulb and electric heater rely, and is reflected in the familiar physical relationship V = IR.
During the 1730s the work of the French chemist Charles de Cisternay du Fay developed the gold-leaf electroscope and proposed that electricity consisted of two types of fluid. He named these resinous and vitreous fluids to describe their origins. In the 1740s the American polymath Benjamin Franklin proposed that these were not separate fluids but a single fluid with a positive or negative excess. The Irish physicist George Stoney refined this, suggesting that positive and negative charges consisted of atom-like particles and that a fundamental charge existed. In 1881 he coined the term electrolion to describe the negative charge carrier. This was later changed to electron. The discovery of the electron subsequently led to a deeper understanding of the causes of electrical resistance. A flow of current is essentially caused by a resistance to the flow of electrons as they encounter the ionic and molecular structure of the conductor through which they move. This phenomenon is indeed a mixed blessing, and despite its usefulness when it comes to heating and lighting one’s home, it has proven to be a limiting factor in electrical and electronic circuit design, resulting in significant losses of energy. The limitations linked to electrical resistance were considered unavoidable for decades until the advent of ultracold temperatures. At end of the 19th century and start of the 20th century, the Scottish chemist James Dewar developed the first practical refrigeration system based on the effects of expanding vapours (Joule-Thomson effect). He and John Fleming predicted that when metals reach absolute zero, electrical resistance would completely disappear. Testing this theory became a reality when Heike Onnes first liquefied helium at a temperature of -268.95 °C (ie. 4.2 K - Kelvin) and then went on to discover that at a temperature of -268.94°C (ie. 4.19 K) mercury lost all its electrical resistance. He had discovered superconductivity and was awarded the 1915 Nobel Prize for physics.