Does the electromotive force (always) represent work?
  In the literature of Electromagnetism, the electromotive force of a "circuit" is often defined as work done on a unit charge during a complete tour of the latter around the circuit. We explain why this statement cannot be generally regarded as true, although it is indeed true in certain simple cases. Several examples are used to illustrate these points. 
C. J. Papachristou, A. N. Magoulas
physics.class-ph