- Joule's Law -
-        1840       -

Simply stated, Joule's Law relates how heat is dissipated by a resistor. Joule's Law states that the heat given off is equal to the square of the current multiplied by the resistance of the resistor and the amount of time passed.

This law also relates itself to Thermodynamics, stating that "at constant temperature the internal energy of an ideal gas is independent of volume."1
The following image shows how this experiment is done today: