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| Cards return |
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| Documents |
| EFFECT JOULE |
| Chronology |
| Scientists index |
| Bibliography |
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| Little
more than twenty years, while
it completes
experiments alternating them to the conduction of
the brewery of the
father, it discovers the law that it determines the heat produced from
the electric current who passes in an electric circuit (“law
of
joule”). The heat, asserts the law, it is proportional them
to the
resistance and the square of the current crosses that it. The law
of
Joule is of fundamental importance for to measure the heat
losses
that happen in every electric circuit (and in order to calculate, on
the contrary, how much heat can be obtained from one stews electrical
worker). Remained unassailable through the times, it will have a single
exception, with the discovery of the phenomenon of the
superconductivity. | | ||||||||
Its search
has been thus important that it has been given its name to an unit of
measure of the job (or the energy), the joule (j). |
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When
a current crosses a
resistance R has the heating of this
last one. It is the Joule effect. The energy quantum W (expressed in
Joule) dissipated in heat in the time t (express in second) depends
from the square of the current and is defined from the relation in
figure. | ||||||||||
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The
phenomenon is
indispensable, as an example, in the filament
of a light bulb to incandescence, in stoves the electrical workers, in
irons from I iron and in the fuses you mail to protection of the
wirings. It is, instead, useless and harmful when the necessity is not
had to produce heat electrically.
In
the members
electrical workers, if the current exceeds the previewed limit, the
Joule effect creates overheating and deterioration of the insulator.
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