James Prescott Joule

READING COMPREHENSION JAMES PRESCOTT JOULE James Prescott Joule (1818-1889) was born in Salford, near and the square of the current Manchester, Great Britain. He studied mainly within the itself. He had thus discovered walls of the family home, was self-taught, and was interested what we now call the Joule effect in electromagnetism (at the time, the main field of study in (or Joule’s first law). physics); his scientific research appeared very meticulous from But the great insights of the the beginning, so much so that in 1839, when he was just 21 British physicist did not stop years old, he constructed a fully functioning laboratory inside there. A brilliant and tireless his home and devoted himself to the study of the efficiency of experimenter, Joule was able to electric motors. So it was that in a short time he became the build mechanical apparatuses with which he demonstrated the greatest expert on the theory of heat of his era. link between heat and mechanical work, and the possibility of After a short period of his life spent in Leiden (in the converting the one into the other, whilst maintaining their sum Netherlands), where he obtained a degree in physics, Joule constant. Joule understood that heat is nothing more than a returned to Salford to manage the brewery inherited from his form of mechanical energy and had thus set the stage for the first father, while still continuing to cultivate his passion for science. law of thermodynamics and for the principle of conservation of In 1841 he sent an article entitled On the production of heat by energy for thermodynamic systems. voltaic electricity to the Royal Society, in which he demonstrated that a conductor, crossed by an electrical current, produces a Can you make a list of appliances that exploit the Joule quantity of heat proportional to the resistance of the conductor effect in their operation? EXERCISES 1 True or false? 3 Match questions and answers. a. James Prescott Joule was an expert on heat QUESTIONS ANSWERS theory. T F A. Why was the young 1. He used a weight attached b. B. His only scientific achievement was the Joule interested in to a string that, falling, Joule effect. T F electromagnetism? caused a paddle immersed c. He gave up science to concentrate on his in water to rotate (Joule apparatus brewing business. T F ). This showed d. that the gravitational He laid the foundations for future advances in potential energy lost by a . T F thermodynamics weight in falling is equal to the internal energy gained 2 Complete with: by the water. proportional • thermodynamics • conservation • converting • B. Why is Joule’s first 2. Joule was not only heat • thermodynamic • conductor • constant • first • law used instead of scientifically minded, he electrical • energy • mechanical • effect Joule effect for his was also very practical: In 1841, Joule demonstrated that a ________, crossed by an discovery regarding he hoped that the family ________ current, produces a quantity of heat ________ to the heat produced by brewing business could the resistance of the conductor and the square of the cur- an electric current? benefit from more efficient electrical engines to rent itself. He had thus discovered what we now call the replace the steam engines Joule ________ (Joule’s first law in English). He also de- it used. monstrated the link between heat and ________ work, and C. What apparatus 3. Because it is ambiguous: the possibility of ________ the one into the other, whilst did Joule use to Joule discovered several maintaining their sum ________. Joule had understood demonstrate the link different physical effects that ________ is nothing more than a form of mechanical between heat and that are often called the ________ and had thus set the stage for the ________ law mechanical work? Joule effect. of ________ and for the principle of ________ of energy for ________ systems. A. _________ B. __________ C. _________ Unità 16 La corrente elettrica continua.

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