Source : Webster's Revised Unabridged Dictionary (1913)

Joule's law \Joule's law\
   1. (Elec.) The law that the rate at which heat is produced in
      any part of an electric circuit is measured by the product
      of the square of the current into the resistance of that
      part of the circuit. If the current (i) is constant for an
      interval of time (t), the energy (H) in heat units equals
      i^{2}Rt, R being resistance.

   2. (Thermodynamics) The law that there is no change of
      temperature when a gas expands without doing external work
      and without receiving or rejecting heat.