# What mechanism happens inside a resistor for potential drop and constant current?

What process happens inside the resistor just after being connected to a battery? I am trying to get a picture of it.

On applying a potential difference, the electric field it generates pushes the electrons to the lower potential end and in the way to the other end these electrons collide with ions and loose energy.

Is it that the electron has zero energy by loss of potential in the form of extra kinetic energy (besides random motion) on leaving the resistor? Is all the energy lost in the resistor? What mechanism causes all the energy to be lost in the resistor and zero energy in form of extra kinetic energy?

• Atoms hold on to the electrons tighter. Oct 25, 2013 at 2:25

Your question rests on a few misconceptions, but it's still a good question.

First, since electrons have negative charge, their actually pushed from the point of lower electrical potential towards a point of higher potential.

Second, we don't normally think of a single electron travelling all the way through the resistor. Many many electrons exist in the material to begin with. When an electric field is applied, they're all pushed together towards the higher potential. Some of them are free to move and so they move.

In fact, the electrons that are free to move are mostly already moving, randomly in different directions. When the field is applied, it just tends to slightly skew the distribution of their direction of motion so that the overall trend is for the electrons to be moving toward the higher potential.

But along the way they're likely to interact with atomic nuclei or other electrons and bounce around, resulting in the randomized motion we just discussed.

Each time an electron "bounces" off an atom in the material, it can give up a bit of its kinetic energy to the atom, and set it vibrating. This vibration can be transferred to the other atoms nearby, and the overall combination of different vibrations is what we experience as heat.

As for whether the electrons that come out the far end (the high potential end) of the resistor still have some kinetic energy (and electrical potential energy), yes they do. And they continue to experience resistance as they (roughly) travel down whatever wire connects them to the + terminal of the battery. But the resistance of the wire is (if the wire is chosen correctly) so small compared to the resistance of the resistor, that we can ignore it for most purposes.

Still the question is not answered.

The current entering a resister is actually opposed by the ions in the resistor. The electrons loses the KE and travels further.The positive side of the battery of the higher potential side will attract all the electrons and forces the electrons to travel at the speed of light further.

This loss in KE is known as the potential drop which is dissipated as heat. Pls remmbr these all happens at a lightning speed. After losing KE, th electrons gain energy as before and travels further as the postive side attracts all the electrons further.

As current is charges per second per unit area,this value is actually lesser than the value with which the electrons entered the resistor.

This value cannot be calculated using a multimeter.

• Electrons travel at the speed of light? The atoms in the resistor are ionized? Current is not "charges per second per unit area", that's current density. Since when did anyone use a multimeter to "calculate" a value, and what exactly is "this value" in that sentence? What does "at lightning speed" mean...lightning is actually pretty slow. Apr 21, 2021 at 11:34