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Happy April Joule's Day

Celebrating April Joule’s Day!

A Few Words from Sara Shepherd, Screaming Circuits Contributing Author...

Today is April 1st - happy April Joules Day!

That’s no joke. Today we’re celebrating the unit of energy called the “joule” and the English physicist who discovered it: James Prescott Joule. Though his formal education ended at the age of fifteen and he never took a course in physics, Joule’s lifelong interest in science and careful observations became the foundation of the First Law of Thermodynamics and the foundation for much of the energy technology we use today.

Born in 1818, the second son of a wealthy brewer, James was considered “delicate” by his mother and homeschooled as a result. Even so, he enjoyed the occasional practical joke. As a child, he was fascinated by electricity and would give electric shocks to his brother as well as to the family servants. When he wasn’t experimenting with DIY circuits (a maker in the 1800'!), the family’s fortune meant James had the privilege of being tutored by some of England’s best teachers, including the famous scientist John Dalton. Dalton’s focus on quantitative experiments left a lasting impression on James.

In 1838 at age fifteen, James had to leave his studies to take over management of the Joule Brewery. Though James now spent his days making beer, he devoted every moment of spare time to continuing his own education through evenings reading and home science experiments. Eventually, his work and scientific hobbies merged and he created a laboratory space within the brewery under the pretense of improving the family business. 

One of James Joule’s first major experiments concerned electromagnetic engines versus steam engines. He believed an electromagnetic engine would be more efficient for the brewery and therefore more profitable, and set out to prove this through a series of experiments.

The results led to the publication of Joule’s first academic paper: “Description of an Electro-magnetic Engine,” published in the Annals of Electricity in 1838. Joule had been disappointed to find that steam engines were actually better at work production than electromagnetic engines. He concluded this was due to the limitations of the electromagnetic engines of the time, and so he turned his attention to improving the performance of electromagnetic engines.

Space nuclear power ship

In an effort to better understand the creation and dissipation of energy, Joule studied a variety of mechanical actions, including the stirring of water by a wooden paddle, expansion of a gas into a vacuum, and the generation of heat sending electrical currents into conductive materials. Twelve years later, Joule’s experimentation resulted in the formulation of the law that now bears his name: Joule’s law.

Joule’s law concerns the mechanical equivalent of heat. He found the heat generated in an electric wire is proportional to the current squared multiplied by the resistance. The law is often written as P=I2R, where P equals power loss, I is the current in amperes, and R is the resistance given in ohms. 

Joule included this law within his paper “On the Production of Heat by Voltaic Electricity”, published in the Proceedings of the Royal Society in 1840. Unfortunately, Joule’s lack of a formal adult education led many to dismiss him as a mere hobbyist.

Undeterred by the scientific community’s lack of recognition, Joule continued his work, now using a paddlewheel and calorimeter to better determine the amount of work required to produce a unit of heat. He concluded that 772.55 foot-pounds of work had to be expended to raise the temperature of one pound of water from 60 °F to 61 °F. 

The results of this experiment were described in his famous 1845 paper “On the Mechanical Equivalent of Heat.” The paper’s findings established that heat and mechanical work are both forms of energy and became the cornerstone of the theory of conservation of energy, the First Law of Thermodynamics.

Despite their earlier dismissals of his work, Joule became a fellow of the Royal Society in 1850 and received the Royal Medal 1852 and the Copley Medal in 1870. In addition, Trinity College Dublin, University of Oxford, and the University of Edinburgh awarded him with honorary degrees. In 1880, the Royal Society of Arts bestowed him the renowned Albert Medal. 

Joule’s work also attracted the attention of William Thomson, better known as Lord Kelvin. Through several years of correspondence and mutual experimentation, the two discovered that when gas is allowed to freely expand, its temperature falls. The pair published their findings and the behavior dubbed “the Joule-Thomson effect,” Their work later enabled the liquefaction of what had been known as “permanent gases.” Liquefaction of gases is the basis of today’s multibillion-dollar industries of refrigeration, air conditioning, and cryogenics.

Joule also carried out extensive research on magnetostriction, observing how ferromagnetic materials modify their shapes when exposed to a magnetic field. 

Joule died at his home in Sale, England on October 11, 1889. His gravestone is inscribed with the number 772.55, his 1878 measurement of the mechanical equivalent of heat.

More than one hundred fifty years after the work was done, his name continues to live on in the physics community both through Joule’s Law and the derived unit of energy or work, the Joule (J), which was named after him.

So, on April Joule’s Day, celebrate not only Joule’s contributions to technology but also the fact that it was all accomplished due to his deep love for physics and commitment to what he called his “serious hobby” of science. Even after winning his first award from the Royal Society, Joule continued to manage the family brewery until 1856! *

We hope the story of Joule inspires any would-be inventors and scientists who feel they don’t have time to pursue their interests. Perhaps you can carve out a part of the day to learn a new skill, set up an experiment, or finally order a prototype of that invention you’ve been dreaming of. 

* Readers who are as invested in beer as they are in physics will be pleased to know that the Joules Brewery continues operations to this day.

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