View source for The Speed of Electricity

It was German physicist Gustav Robert Kirchhoff in the year 1857 who first identified the connection between the speed of light and the speed of electric signals in a conducting wire. Meanwhile, although charged particles in a conductor don’t travel at anywhere near the speed of light, this is not considered to be a contradiction, because it is generally accepted that it is changes in the electric current, and not the electric current itself, that are propagated at the speed of light, the assumption being that a longitudinal compression wave propagates through the electron cloud in the conducting material. 
       The idea of such a compression wave travelling at the speed of light is not however very convincing, because it’s unlikely that such a wave would just happen to propagate through a cloud of outer shell conduction electrons at exactly the same speed as wireless radiation in space, never mind how the same approach would then also apply in an electrolytic conducting solution. This matter will therefore be investigated further.


See,
https://www.researchgate.net/publication/377978571_The_Speed_of_Electricity