Mechanical energy nonconservative forces, like frictional forces, will be present, but often they are of negligible values and the mechanical energy's being constant can therefore be a useful approximation. In elastic collisions, the mechanical energy is conserved but in inelastic collisions, some mechanical energy is converted into heat. The equivalence between lost mechanical energy (dissipation) and an increase in temperature was discovered by James Prescott Joule. Many devices are used to convert mechanical energy to or from other forms of energy, e.g. an electric motor converts electrical energy to mechanical energy, an electric generator converts mechanical energy into electrical energy and a
North University of China and Art 13. Software School 12. Graduate School 13. College of Continuing Education North University of China was authorized by the State Council to confer M.S. degree in 1981 and Ph.D. in 1998. At present, the university has the right to confer M.S. degrees in 20 disciplines, and Ph.D.s in 4 disciplines. The university has 8 provincial and ministerial key disciplines, including Mechanical Manufacturing and Its Automation, Mechatronic Engineering, Test & Measurement Technology and Instrumentation, Materials Processing Engineering, Applied Chemistry, Special Mechanical System and Its Application Engineering, Energy Materials Engineering, and Precision Instrument and Mechanism. Over the years, with conditions