Joule’s Dynamo – The Joule Heating Effect

Dynamo-Circa Early 19th Century

      In Joule’s Experiment With Electricity, the dynamo was powered by a steam engine, which enabled the dynamo’s shaft to spin.    As it spun, the magnet located inside the dynamo also spun, thus creating a rotating magnetic field that surrounded the dynamo’s internal copper wire coils.

      The interaction between the magnetic field and wire produced electric current which flowed inside the coils.   The current ultimately made its way out of the dynamo by way of external wires, to which any number of devices could be powered when attached.   The net result was the engine’s mechanical energy had been converted into electrical.   To learn more about the process of producing electricity with magnets see my blog on, Coal Power Plant Fundamentals – The Generator.

      As electrical energy flowed through the dynamo’s wiring, some of it was converted into heat energy.   This was due to resistance posed by impurities present in the makeup of the wire, impurities which served to impede the overall flow of electric current.   When electrons flowing through the wire collided with these impediments, they caused heat to build up inside the wire, a phenomenon which came to be known as the Joule Heating Effect.   To read more on electrical resistance and Joule heating go to my blog, Wire Size and Electric Current.

      The net result of Joule’s Experiment With Electricity was to further prove the link between chemical, heat, mechanical and electrical energies as set out in the Law of Conservation of Energy.   And I suspect that knowledge was later put to use by Joule’s family for the betterment of their brewery business.

Joule’s Experiment With Electricity

      In my work as an engineering expert I’ve dealt with all forms of energy, just as we’ve watched James Prescott Joule do.   He constructed his Joule Apparatus specifically to demonstrate the connection between different forms of energy.   Today we’ll see how he furthered his discoveries by building a prototype power plant capable of producing electricity, a device which came to be known as Joule’s Experiment With Electricity.

                      Joule’s Experiment With Electricity

      As the son of a wealthy brewer, Joule had been fascinated by electricity and the possibility of using it to power his family’s brewery and thereby boost production.   To explore the possibilities, he went beyond the Apparatus he had built earlier and built a device which utilized electricity to power its components.   The setup for Joule’s experiment with electricity is shown here.

      Coal was used to bring water inside a boiler to boiling point, which produced steam.   The steam’s heat energy then flowed to a steam engine, which in turn spun a dynamo, a type of electrical generator.

      Tracing the device’s energy conversions back to their roots, we see that chemical energy contained within coal was converted into heat energy when the coal was burned.   Heat energy from the burning coal caused the water inside the boiler to rise, producing steam.   The steam, which contained abundant amounts of heat energy, was supplied to a steam engine, which then converted the steam’s heat energy into mechanical energy to set the engine’s parts into motion.   The engine’s moving parts were coupled to a dynamo by a drive belt, which in turn caused the dynamo to spin.