Have you ever wondered why

Have you ever wondered why?

Radio waves are made and how they fly,

Making possible myriad applications,

Ranging from the internet to radar or even microwave ovens.

The story is very old,

Of Maxwell, Faraday, Coulomb, Volta, Ampere, Oersted, Ohm, Tesla, Franklin, other greats whose feats are all gold.

Volta invented the battery and produced the flow of charge called electric current,

Oersted discovered soon after that this flow in a straight wire,

caused a circular magnetic field, in the perpendicular plane, to be present.

Faraday discovered that a changing magnetic field through, say, a coil produced a voltage that is a source of electric field.

Very important outcomes did this finding yield.

It was left to Maxwell to realise that a changing electric field across a condenser

with a dielectric within, produced a displacement current, which we will soon explain;

For now we notice it produced a magnetic field: Oersted all over again.

Now a capacitor we do recall, consists of two parallel conducting plates separated by an insulator,

which when connected to a battery, a DC voltage generator,

stores charge on its plates the quantity being proportional to the voltage applied.

This is like the common rubber balloon which can store a volume of air depending on the pressure pumped inside.

Thus when an alternating voltage is applied to a capacitor,
we see the positive charge on the top plate and the negative in the bottom one increase as the voltage rises and decrease as it falls.

This amounts to a conventional positive charge current flowing in the connecting wire from the bottom plate to the top one when the voltage rises and from the top plate to the bottom when it falls,

despite the fact no charge can flow across the condenser, because its plates are separated by an insulator in between.

This changing electric field then is what displacement current is about,

All very clear without any doubt.

Thus in a wire if an oscillating current does flow,

A circular, also time varying magnetic field we find to grow.

Now this changing magnetic field will produce still further a perpendicular changing electric field as per Faraday’s law.

Which will lead to a displacement current giving rise to a changing magnetic field again and further beyond,

And a wave propagates ahead on and on.