Transient energy is energy that exists only during a transfer process from one stored energy to another. There are two forms of transient energy: heat and work. These cannot be stored like other forms of energy, such as potential energy; i.e., a hot object does not, by itself, stay hot. Its heat will flow away spontaneously. If a book is lifted from the floor to the table, work is being done to move it; but once the book is placed on the table, all of the work has been converted to potential energy.

Work is an energy transfer due to a potential difference other than heat. It can be observed in many different forms, such as mechanical work, expansion and compression work, and work done on charges in a magnetic or electric field. Mechanical work done by a constant force, F, acting through a distance...