A decrease in potential energy means the body does work on something else, e.g., a failing piledriver against a stake. 28.The K.E. of random motion of atoms and molecules of a substance manifests itself as heat. The Temperature of the substance is a direct measure of this random molecular energy. Electrical charges are subject to a force law very similar to that of gravitation though both repulsion and attraction are allowed. Moving electrical changes constitute an electric current.
Electric currents produce magnetic forces upon other electric currents.
If we wish to keep these conservation laws, we must believe in fields which carry energy and momentum. Unlike particles, waves can show destructive as well as constructive interference, i.e., the presence of two or more wave sources can result in less wave energy at a point then that due to one of the single sources. Two periodic waves of the same type and frequency, coming from the same source, will interfere constructively at a point when the difference in distance they have traveled from that source equals a whole number of wavelengths. This is very commonly noticed with sound and water waves. 41.Lorentz and FitzGerald gave an ad-hoc explanation of the failure of Michelson and Morley to detect motion with respect to the electromagnetic medium by saying that matter physically shrank in the direction of motion since all matter was held together by electrical forces.