Hopkinson, John

John Hopkinson was born July 27, 1849 in the city of Manchester . Even before reaching the age of 16, he attended lectures at Owens College, and at the age of 18 he was able to receive a mathematical scholarship to study at Trinity College Cambridge, where he graduated. He graduated from Cambridge in 1871, receiving upon graduation the title of “Senior Wrangler” (the highest mathematical title in the Cambridge educational system for students) and the first Smith Prize; even before completing his studies at Cambridge, he was simultaneously studying at the University of London , where he received a bachelor of science degree and where he had a Whitworth scholarship.

After completing his education, he was appointed one of the employees of the University of Cambridge and a teacher in it, however, he did not spend much time on teaching work, since he was more attracted to studying the practical side of engineering; in his experiments, his father helped him. Already in 1872 he received the position of technical director at the glass manufactories of Messrs Chance Brothers & Co in Birmingham. Six years later, he moved to London, where, while remaining a scientific adviser to the Chance brothers on technical issues, he made a successful career as a consulting engineer. His work dealt mainly, although not exclusively, with issues related to electrical engineering , primarily as an expert witness in patent filing. In 1890, he was appointed director of the Siemens Laboratory at King’s College in London as a professor of electrical engineering, and then received the title of professor. His death in 1898, together with his son and two daughters, occurred as a result of an accident in the Swiss Alps , the exact nature of which was never ascertained.

Most of the research and scientific work of Hopkins was devoted to electricity and magnetism, electrodynamics, and in particular electrical engineering : electric motors and dynamos , design of AC systems and transformers , power transmission, magnetic circuits, hysteresis, and so on. The scientific works written by him have a volume of about 60 sheets.

Hopkinson discovered the phenomenon of a sharp increase in the magnetic permeability of ferromagnets in a weak magnetic field near the Curie point , which was named after him the Hopkinson effect . Together with his brother Edward ( Edward Hopkinson , 1859-1922) he developed a general theory of magnetic circuits (the mathematical formulation of the theory derived by the brothers was called the Hopkinson formula or Hopkinson’s law , an analogue of Ohm’s law), and he also formulated the theory of variable currents and magnetic flux . Already during his work in Birmingham, he developed diopter methods for the concentration of a ray of light emanating from a lighthouse; at the same time, working as the technical director of glass manufactories, he studied the refractive indices of various types of glass. He conducted many experiments and observations of magnetization, studying iron, nickel and various alloys of two elements, which at the same temperature were in magnetized and demagnetized states. He actively contributed to the spread of electricity in everyday life, in 1878 he proposed an improved design of the dynamo. In 1884, he designed the first transformer with a closed magnetic system, called the Hopkinson transformer. He was also the first to substantiate the possibility of parallel connection of working engines. He conducted research in the field of electrostatics .

• Hramov Yu. A. Hopkinson John ( Physicists: Biographical Reference / Ed. A.I. Akhiezer . - Ed. 2nd, rev. and add. - M .: Nauka , 1983 .-- S. 90 .-- 400 p. - 200,000 copies. (in per.)
• This article (section) contains text taken (translated) from the eleventh edition of the Encyclopedia Britannica , which went into the public domain .