Physics – Condensed Matter – Other Condensed Matter
Scientific paper
2004-07-29
American Journal of Physics 73 (2005) 302
Physics
Condensed Matter
Other Condensed Matter
accepted for publication in American Journal of Physics (to be published between February 2005 and June 2005)
Scientific paper
10.1119/1.1848114
We show how a simple laboratory experiment can illustrate certain electrical transport properties of metallic granular media. At a low critical imposed voltage, a transition from an insulating to a conductive state is observed. This transition comes from an electro-thermal coupling in the vicinity of the microcontacts between grains where microwelding occurs. Our apparatus allows us to obtain an implicit determination of the microcontact temperature, which is analogous to the use of a resistive thermometer. The experiment also illustrates an old problem, the explanation of Branly's coherer effect - a radio wave detector used for the first wireless radio transmission, and based on the sensitivity of the metal fillings conductivity to an electromagnetic wave.
Castaing Bernard
Falcon Eric
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