Johan Carl Wilcke (6.09.1732-18.04.1796) was a Swedish physicist and a member of the Royal Swedish Academy of Sciences, from 1784 its permanent secretary. He was born in Wismar. He graduated from the University of Rostock (1757). From 1759 he worked in Stockholm.
He carried out experimental research on electrical and magnetic phenomena and on heat. He performed a number of experiments with the Leyden jar (1757). He observed (1758) the polarisation of dielectrics. He produced (1766) the first map of magnetic inclination. In 1772 he repeated G. W. Richmann's experiments and checked the formula for the temperature of a mixture. He made the first measurements of the heat capacities of solids (1772). He proposed two methods of measuring heat capacity — the method of mixtures and a method based on melting ice with the hot body under study. He introduced the concept of the “water equivalent”. He helped to establish correct ideas about the physical meaning of calorimetric concepts. Independently of A. Brugmans he put forward (1778) the two-fluid hypothesis of magnetism.