Visualization of induced electric fields

A cylindrical electrolytic tank between a set of Helmholtz coils provides a classroom demonstration of induced, nonconservative electric fields. The field strength is measured by a sensor consisting of a pair of tiny spheres immersed in the liquid. The sensor signal depends on position, frequency, and orientation. A low resistance copper ring strongly modifies the magnetic field inside and increases the field outside; the electric field changes accordingly. A metallic ring with a small gap can be used to measure the behavior of the electric field in the vicinity of windings around a transformer core. The measured results are consistent with simple models.