Changes

where <math>\mathrm{d}U</math> is the infinitesimal increase in the internal energy, <math>\delta Q</math> is the infinitesimal amount of heat added, and <math>\delta W</math> is the infinitesimal amount of work performed.

where <math>\mathrm{d}U</math> is the infinitesimal increase in the internal energy, <math>\delta Q</math> is the infinitesimal amount of heat added, and <math>\delta W</math> is the infinitesimal amount of work performed.

Note that if no energy is added, then the maximum amount of work that can be performed by the system is equal to its initial energy.  This prevents the existence of a type of [[perpetual motion machine]].

Note that if no energy is added, then the maximum amount of work that can be performed by the system is equal to its initial energy.  This prevents the existence of a type of [[perpetual motion machine]], along with preventing fractiation in the monkey.