We all know that light is an electro magnetic wave. but is electricity a EM wave? If it is then why light does not requires a medium to travel and why on the other side electricity needs a conductor ( I mean a medium) to travel. WHY? Or HOW?
Electricity, understood as movement of electrical charges, can generate an EM-Wave, if the geometric conditions of the circuit and frequency conditions in the current flow are given.
electricity is refered to the energy carried by electric current. EM are generated by accelerating charge particles e.g. in a dipole antenna when given an AC voltage input. The energy of current is transmitted as EM waves.
The question of this kind always rises when we compare light waves with other kinds of mechanical waves say sound waves. And the answer can be Aether, if you mean by medium some physical thing , is the medium through which light travels. Alas ether is not founded yet.
One can never tell why. One can only tell you how.
$2$ Book: THE EVOLUTION OF PHYSICS by Albet einstien and leopold.
There are many more good articles about aether. Those i've mention are those which i'have read so i can promise you that these are good explainations to the best of my knowledge.
"In several parts of this treatise an attempt has been made to explain electromagnetic phenomena by means of mechanical action transmitted from one body to another by means of a medium occupying the space between them. The undulatory theory of light also assumes the existence of a medium. We have now to shew that the properties of the electromagnetic medium are identical with those of the luminiferous medium." - Maxwell
Maxwell's displacement current is a physical displacement of the aether.
A light wave is an aether displacement wave.
Aether has mass, physically occupies three dimensional space and is physically displaced by the particles of matter which exist in it and move through it.
Displaced aether pushing back and exerting inward pressure toward matter is gravity.
The state of displacement of the aether is gravity.
A moving particle has an associated aether displacement wave. In a double slit experiment the particle travels through a single slit and the associated wave in the aether passes through both.