A changing flux induces an emf, or potential difference, in a loop. Whenever we have a potential difference we have an electric field. If the potential difference is the induced emf, we get:

ε = ∫ E ds

The integral should be carried out over a closed loop so we can bring in the changing flux in that loop:

ε = -dΦ_B/dt

This gives, integrating around a closed loop, the general form of Faraday's Law:

∫ E ds = -dΦ_B/dt

Electric fields produced by changing magnetic fields have some interesting properties:

• the electric field lines are continuous loops
• the electric field is non-conservative