where E is the entire electric field, conservative and non-conservative, and the integral is around an arbitrary, but stationary, closed curve C through which there is a time-varying magnetic flux Φ Φ C , and A is the vector potential. The electrostatic field does not contribute to the net emf around a circuit because the electrostatic portion of the electric field is conservative (i.e., the work done against the field around a closed path is zero, see Kirchhoff's voltage law, which is valid, as long as the circuit elements remain at rest and radiation is ignored). That is, the "induced emf" (like the emf of a battery connected to a load) is not a "voltage" in the sense of a difference in the electric scalar potential.