Page:Outlines of Physical Chemistry - 1899.djvu/200

 182 OUTLINES OF PHYSICAL CHEMISTRY

��H. ELECTRO-CHEMISTRY

Any form of energy can be expressed by the product of two factors, one representing the quantity, the other representing the intensity. When an object is raised to a certain height above the ground, the potential energy which it acquires is expressed by p x e, i.e.. the weight of the object (intensity of the resistance overcome) multiplied by the height through which the object has been raised. If the object be allowed now to fall, it arrives at the ground with the velocity v, and its kinetic energy is expressed by

-£-, where m denotes its mass. We know that ^- ifl

equivalent to p x e.

The increase of energy which a body experiences on having its temperature raised through a certain number of degrees is equal to the caloric capacity of the body (quantity) multiplied by the rise in temperature (intensity).

In the same way, to determine the energy developed by an electric current we must consider the quantity of elec- tricity which passes and its loss of tension or fall of potential.

Ohm's Law. — Let us consider the part of the con- ductor between a and b.

! ! !

I l I

AC B

The intensity of the current, that is to say, the quantity of electricity, 1 which passes through any section whatever c, in one second, is proportional to the active electro- motive force 2 and inversely proportional to the resistance

the metallurgical transformations brought about at high tempera- tures, many are endothermic.

1 It may be mentioned that the term current-intensity or current- strength is the quantity-factor of electrical energy.

2 That is to say, proportional to the fall of potential between a and b.

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