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Joule and Ramsey: How an experiment in the 1840s changed the theory of thermal energy
In the early 19th century, the nature of heat energy remained a mystery to science. Traditional heat theory holds that heat is a substance (called "therogen"), but this view has undergone a subversive change with the experiments of Joule and Lanzi. This article will delve into how the experiments of these two scientists in the 1840s led to major changes in thermal energy theory and laid the foundation for subsequent scientific development.
Joule’s Experimental Exploration
James Prescott Joule published research in 1840 that overturned the prevailing caloric theory at the time. In his experiment, he conducted an electric current through a length of metal wire and observed that the temperature of the water increased. This experiment showed that the flow of electric current generates heat, which he called "Joule heating." This confirms that heat is not an independent substance, but a conversion of energy forms.
"Heat is a form of energy, not a substance."
Lan Qi’s contribution
Heinrich Lenz conducted independent research on Joule and proposed a similar theory of heat generation in 1842. Lanzi confirmed that the generation of heat is proportional to the square of the current and the resistance of the material, a discovery that became known as the "Joule-Lantzi law." Lan Qi's research not only consolidated Joule's experimental results, but also helped establish the mathematical relationship between electric current and thermal energy, giving the entire scientific community a deeper understanding of thermal energy.
Microscopic description of Joule heat
Joule heating is a microscopic phenomenon that results from the interaction of charged particles (usually electrons) with matter in a conductor. When there is a voltage difference in space, the electric field accelerates the electrons, increasing their kinetic energy. During their movement, these electrons collide with ions in the conductor, transferring energy to the ions, causing them to oscillate. These oscillations are the source of the "heat energy" we measure.
Applications of Joule heating
Joule heating now plays an indispensable role in many applications, such as: electric heaters, induction cookers, welding equipment, etc. In the field of food processing, Joule heating is used for rapid and uniform heating, especially for food containing particles, which has higher electrical conductivity and can improve heating efficiency. During this process, heat is released when electric current passes through the food, thus achieving the effect of food sterilization.
The impact of the scientific revolution
The research of Joule and Lanzi not only changed the understanding of the nature of thermal energy, but also had a profound impact on the subsequent development of engineering and technology. The principle of Joule heating became the basis of electronic equipment, power transmission and other technologies. During the scientific revolution at the end of the 18th century and the beginning of the 19th century, these discoveries not only overturned the past caloric theory, but also provided an important theoretical basis for the law of conservation of energy.
Modern technology and future prospects
With the advancement of technology, the application scope of Joule heating is no longer limited to traditional electrical appliances. Its principles are also widely used in emerging fields such as e-cigarettes and medical equipment. In the future, the potential of Joule heating will help develop more efficient and environmentally friendly energy technologies, all stemming from those pivotal experiments in the 1840s.
The scientific research achievements of Joule and Lanzi not only shaped the current understanding of thermal energy, but also inspired countless scientists in the future to explore and explain the mysteries of nature. As we face energy challenges today, we may want to think about: How will these early scientific discoveries continue to inspire us to solve future energy problems?
