As an adult, Joule managed his father's brewery. Science was merely a serious hobby. Sometime around 1840, he started to investigate the feasibility of replacing the brewery's steam engines with the newly invented electric motor. His first scientific papers on the subject were contributed to William Sturgeon's Annals of Electricity. Joule was a member of the London Electrical Society, established by Sturgeon and others. Motivated in part by a businessman's desire to quantify the economics of the choice, and in part by his scientific inquisitiveness, he set out to determine which prime mover was more efficient. He discovered Joule's first law in 1841, that the heat which is evolved by the proper action of any voltaic current is proportional to the square of the intensity of that current, multiplied by the resistance to conduction which it experiences.[3] He went on to realize that burning a pound of coal in a steam engine was more economical than a costly pound of zinc consumed in an electric battery. Joule captured the output of the alternative methods in terms of a common standard, the ability to raise a mass weighing one pound to a height of one foot, the foot-pound.
By the time of Joules research, coal fired steam engines were in development for over 100 years. Coal had become less expensive with time, as engine improvements added efficiency.
William Jevon noted that this improved efficiency actually resulted in more energy use, not less. Less expense allowed coal to be employed in more frivolous endeavors, such as rail transportation. It posed a paradox!
” He went on to realize that burning a pound of coal in a steam engine was more economical than a costly pound of zinc consumed in an electric battery. “
Bears application to the current debate of the economic value of renewable energy, electric cars versus “fossil fuel” use.