Sunday, July 21, 2019

electricity - What is the reason for extremely high speed of electric current?


I know that electric current is the flow of electrons but electrons have a very slow drift speed (about 2mm/s). How is it that electric current reaches its destination at almost the speed of light?



Answer



The speed at which the signal in a circuit travels is not the speed of drifting free electrons but rather the speed of electromagnetic waves whose velocity factor is usually $0.5$ to $0.99$(50%-99% $c$).


Therefore, the speed of electric signal is the speed of the propagation of the electric field waves of the conductor but not the drift speed of the free electrons drifting through the conductor.



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