Physics. Named after James P. Joule, 1818-1889. Joule, abbreviated J, is the SI unit of electrical, mechanical, and thermal energy. One joule is equal to the work done when a force of one newton acts through a distance of one meter. 1 J = 1 N·m = 1 W·s = 1 kg·m2·s--2. One joule is equal to 0,239 calories.