Here's what I think the motion of electrons would be like.

Let's say the electrons were initially at rest. Now, when the voltage starts increasing, the electrons start accelerating faster till the voltage reaches its maximum value. When the voltage starts decreasing to zero, the electron's velocity is still increasing but the acceleration is decreasing. When the voltage reaches zero, the electrons experience no acceleration but it's still moving with some velocity. Now, as we're talking about AC condition, the voltage reverses its polarity and this causes the velocity of the electrons to slow down real fast. After the voltage reaches its maximum value (negative), it starts increasing to zero. This causes the electrons to lose its velocity slowly as the acceleration (negative) is decreasing and when the voltage reaches zero, the electrons are at rest. Then this pattern keeps repeating. So, in a way, the electrons move in the same direction in an alternating current but it moves and stops repeatedly.

Is this thinking correct or am I wrong somewhere?

  • $\begingroup$ It sounds as if you expect there to be some net movement of electrons in the "positive" direction in an AC circuit. But which direction is "positive?" Voltage is what makes the electrons move, and the average voltage over any whole number of cycles in a "pure" AC circuit is zero. $\endgroup$ – Solomon Slow Dec 3 '19 at 14:29

Your thinking is basically correct, except that the electrons in a wire don't "move real fast" anyway.

In a domestic electricity supply, each electron is only oscillating a fraction of a millimeter back and forth at 50 Hz. The "thing" that is being transmitted from the power station to your house is the chain of electrostatic forces acting when two electrons try to move closer together, not large movements of the electrons themselves. The electrostatic forces between two electrons are many orders of magnitude greater than the inertia forces needed to physically move and accelerate the electrons.

| cite | improve this answer | |
  • $\begingroup$ Even under a DC voltage, electron scattering makes them move quite randomly (diffusion) with only a small field-induced bias (drift) to their overall movement. $\endgroup$ – Jon Custer Dec 3 '19 at 15:01

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.