Vector Potential Coil and Transformer

We demonstrate a vector-potential coil and a vector-potential transformer that each use a long flexible solenoid wound around a hollow cylinder. The long flexible solenoid has a current-return wire that runs through the core of the solenoid itself. These devices generate a curl-free vector potential in the hollow cylinder without a magnetic field. In the space within the cylinder where no magnetic field exists, the vector potential is detected by observing a voltage across a secondary conductor that is proportional to the time rate of change of the primary current. We also present the transparency properties of the vector potential through a thick metal whose thickness is larger than the skin depth at the test frequency.