Joule (James? Pre-classification? Joule, 18 18 ~ 1889) is an outstanding physicist in Britain. 18 18 65438+ was born on February 24th. From 1840, Joule began to study the thermal effect of current, and wrote papers such as "On the Heat Produced by Voltaic Electricity" and "The Heat Released by Metal Conductors and Batteries in the Process of Electrolysis", pointing out that the heat generated by a conductor in a certain period of time is directly proportional to the square of current and the product of conductor resistance. Shortly thereafter, 1842, the famous Russian physicist Lengci independently discovered the same law, so it was called Joule-Lenz Law. He did more than 400 experiments in different ways and came to the conclusion that the mechanical equivalent of heat is a universal constant, which has nothing to do with the way of doing work. Later, people realized that this value was 427 kg/kcal. In 1850, he published an article on the mechanical equivalent of heat.

On July 2 1 65438, Danish physicist Oster published a paper entitled "Experiment of Current Collision on Magnetic Needle", reported his experiment, and announced the magnetic effect of current to the scientific community. As an epoch-making day,1820 July 2 1 went down in history, which opened the prelude of electromagnetism and marked the arrival of the era of electromagnetism. Oster discovered the magnetic effect of current. Ampere (A.M.Ampere, 1775- 1836) repeated Oster's experiment and developed it. /kloc-in September, 2008, he reported his first paper to the French Academy of Sciences, expounded his repeated experiments on the magnetic needle with current, and put forward the possibility that circulation can produce magnetism. In this experiment, Ampere found that the relationship between the direction of magnetic needle rotation and the direction of current obeys the right-hand rule, which is later called Ampere's right-hand rule.