Physics

What is the speed of the electric current?


When you turn on a switch that turns on a light, you are actually just causing a circuit to close. At this point, the free electrons in your home's wiring will be influenced by an electric field and begin to move. This is the electric current.

But have you ever wondered how fast these infinitely small particles move so that the lamp turns on practically the moment it is turned on?

The first thought that comes to mind is that the electrons travel the conductor segment between the switch and the lamp in a tiny fraction of a second, leading us to think that the speed of travel of these electrons is close to the speed of light. .

In fact, this reasoning leads to a big mistake.

To arrive at the right answer, we must think that the conductor wire, which is usually copper, is made up of infinite atoms from its beginning to its farthest end.

Therefore, closing the circuit by pushing the switch causes all free electrons to move. Not necessarily the electrons that are close to you are the ones that will make the lamp work.

Surprisingly, the velocity of each electron is really slow, experimentally results in close to 1 cm / s varying depending on the conductor material and the characteristics of the location.

And if we think that the networks in Brazil have alternating character, with frequency of 60 Hz (that is, the direction of the current movement changes 120 times every second), we will probably conclude that it is possible that the free electrons that are close your hand at the moment you push a switch may never cross the entire wire segment to the point where they actually reach the lamp to which it is turned on.