To understand what Maxwell did that shocked the world of electrical physics, we must begin with a brief discussion of the basic internal parts of a capacitor. A plate of metal (conductor) is separated by a slab of insulating material (dielectric) and another plate of metal (second conductor). If we charge a capacitor up, and then connect a wire from plate A to plate B, an electric current will flow through the wire. Around the wire is an electrical field. All of the negative charge on plate A will pass through the wire and cancel out all of the charge on plate B. At the exact point in time when the plates become charge less through cancellation, no electric field exists between the plates. However, the magnetic field surrounding the connecting conductor which was produced by the current is still present. Faraday's Laws clearly state that every magnetic field has to have an electric current associated with it at the same point in time. This lack of symmetry bothered Maxwell. He decided to try to use his knowledge of geometry to try to explain this strange phenomena.

Another problem that troubled Maxwell was the discontinuity of the space surrounding the conductor (a magnetic field present) and the space between the capacitor plates (no electrostatic field present).

To attempt to eliminate these discontinuities, Maxwell came up with the idea that the decreasing electrostatic field between the capacitor's plates and the current building up in the conductor was a current not in a conductor, but in a vacuum. He called it a “displacement current.” This displacement current actually separates from the conductor and generates a magnetic field with its lines of force circling the lines of force of the electric field.

As the field collapses on the conductor, a current of opposite polarity is generated which charges the capacitor's plates to opposite the original polarity. This process repeats over-and-over each time thus producing an alternating field of opposite polarities and recharging the capacitor's plates again (also to the opposite polarity each time). We have the electrical equivalent of a mechanical oscillator.

Kinetic (dynamic) energy is stored in the magnetic field created by the current, which again becomes the potential energy of the capacitor's plates with reversed polarity. The electrical inertia of the electrons in the moving charge causes these charges to continue moving past the zero (neutralized) point and recharge the capacitor's plates to opposite polarity.

Like a large mechanical pendulum, the smaller the physical geometry of the capacitor the faster it recharges, and hence, the faster it will oscillate. The self-magnetic field the current builds up acts like a retardant and slows the oscillations in larger capacitors. The old culprit here is again Mr. Newton's property of matter called inertia which effects even subatomic particles such as electrons.

There is an important difference between oscillating currents in a capacitor and a mechanical pendulum bob - and this particular difference is what Maxwell zeroed in on with his brilliant mathematical theory. A swinging mechanical pendulum will eventually lose all of its energy through heat losses (friction) in the supporting bearing. However, even if the friction in an oscillating capacitor-inductor circuit (the inductance comes from the conducting wire we discussed) is reduced to zero (as in the case of superconductivity), the capacitor loses almost all of its energy very quickly - it becomes electromagnetic radiation and travels off in space.

Maxwell became very intrigued with the fact that this energy was disappearing! He wanted to know where it was going and how it was getting to where it was going. What was the mechanism to explain this strange loss of electrical energy?

His shocking conclusion here is that these interlocking fields actually physically separate from the conductor and travel off into space. Each separate magnetic field has an associated electrostatic field which in turn produces another magnetic field which produces another electrostatic field...ad infinitum.

The displacement current of the capacitor is linked with a magnetic field and this magnetic field generates another displacement current which in turn generates another magnetic field, etc. The key genius here is that Maxwell recognized that space itself (a high vacuum) could support a displacement current and a physical copper conductor is unnecessary. Imagine that - an electrical current flowing through an insulator!

Each interlinking and alternating chain of electrostatic fields and magnetic fields physically repel (due to their opposite polarity) each other and push them out into space. An oscillating field of electric and magnetic force becomes electromagnetic radiation and travels through free space without a conducting medium. In short, A displacement current does not require a conventional conductor which is in sharp contrast with the electric and magnetic fields in Mr. Faraday's transformer functioning on conventional elements of electromagnetic induction. Maxwell's original work sought only to offer a clear explanation to the mechanism of the capacitor. However, when he finished his mathematical equations he discovered some surprising elements he had not considered.