01-11-2004, 05:54 PM
|
|
|
So Fucking Banned
Join Date: Oct 2003
Location: icq: 121189
Posts: 18,889
|
Quote:
Originally posted by bogo
joule essentially? never heard of him..
|
on the bulb:
Quote:
|
The solution lay not in an electrical arc in open space, but in electricity passed through a filament. The breakthrough theory became known as the Joule effect after James Prescott Joule, who theorized that electrical current, if passed through a resistant conductor, would glow white-hot with heat energy turned to luminous energy. The problem was devising the right conductor, or filament, and inserting it in a container, or bulb, without oxygen because the presence of oxygen would cause the filament to burn.
|
on joule:
Quote:
English physicist who was initially interested in the efficiency of electric motors. He discovered the heat dissipated by a resistor is given by Q = I2Rt (where I is the current, R the resistance, and t the time ), a result now known as Joule's law.
Motivated by theological beliefs, Joule began attempting to demonstrate the unity of forces in nature. He determined the mechanical equivalent of heat by measuring change in temperature produced by the friction of a paddlewheel attached to a falling weight in the 1840s. He made a series of measurements and found that, on average, a weight of 772 pounds falling through a distance of one foot would raise the temperature of one pound of water by 1° F. This corresponds to (772 ft lbs)(1.356 J/ft lb) = 59 453.6 Calories, or 1 cal = 4.15 Joules, in close agreement with the current accepted value of 1 cal = 4.184 J. Joule was not the first person to establish the mechanical equivalence of heat, but it was his demonstration that eventually came to be accepted. He did not claim, however, to have formulated a general Law of Conservation of Energy. Nevertheless, his experiments were certainly fundamental in bringing that formulation about. In addition, Joule's experiments showed that heat is produced by motion, contradicting the caloric theory.
|
|
|
|