Electrical Energy: Is Kinetic Energy of Electrons Involved?

In summary, the conversation discusses the relationship between electrical energy and the kinetic energy of electrons. While there is some debate on the exact mechanics of how electrical energy is transferred, it is generally agreed that electrical energy is due to the electric field and is similar to gravitational potential energy. Different components in an electric circuit store and dissipate energy in different forms, such as electric fields, magnetic fields, and chemical bonds. The concept of resistance is also discussed, with the idea that classical reasoning of electron collisions and rapid electron motion yield incorrect results. Overall, it is agreed that electrical energy is not solely in the kinetic energy of electrons, but rather is a combination of different forms of energy.
  • #1
tushar gupta
10
0
Does electrical energy reside in kinetic energy of electrons?
 
Physics news on Phys.org
  • #2
No. At least not a significant amount in ordinary circuits.
 
Last edited:
  • #3
hhhmmm, never quite occur to me to look at it that way...

but now that you mention it, maybe it is better to equate electrical energy to some kind of potential energy, though, not kinetic...after all, when you get some work out of some electrical device through which a bunch of electrons are going by (or back and forth), the electrons actually do not loose any speed!

so, the energy pushing the electrons is some potential energy behind them...in a toy that works on batteries, the electrons are pushed by some chemical potential energy stored in the battery...at home, the potential energy is the voltage, etc.

does this make sense?
 
  • #4
you said that electrons don't lose speed.but i thought the moving electrons collide with the nucleas of the matter which gives them vibrations and that vibration is turned into heat(for a resistor).
that is why i had this doubt whether electrical energy is in the kinetic energy of the electrons..

nevertheless thanks for replying.
 
  • #5
Well, I am not going to say that I am 100% sure of what I have stated...I was just going for some kind of analogy, anyway.

Then again, imagine your house, at the electric company meter they measure how much current you are using...there are two wires, whatever current goes in one wire, comes out the other...they are equal...

does not matter how many paths there are in the house for the current to follow, whether they are "easy" paths or difficult ones (very resistive like an incandescent light bulb)...at every node where the current could split in two, the current is the same when those two paths get back together...

you see what I am going with this? It seems as if current is always flowing at the same speed no matter what the load is.

that is not to say that for a resistive element there are no collisions, you are correct in that respect...but it does not look like these collisions slow down the electrons that much...

or put another way, in order for the collision to not slow down electrons that much, you have to find a balance in how many electrons you want to send through and how much force (voltage) you use to push them...this is Ohm's Law: V=IR ...if you keep the voltage constant and up the resistance, then the amount of electrons going through go down...since there isn't enough push to handle the same amount of collisions...

does this help?
 
  • #6
as for the velocity of current, look up drift speed... there's a formula: I=nAQv, where v is the electron drift speed.

Electrical energy is due to the electrical field, much like gravitational potential energy.

for a given electric field E, the energy density is given by

u=[itex]\frac{\epsilon_{0}|E|^{2}}{2}[/itex]

hope this helps
 
  • #7
I actually remember deriving this in my AP physics class. It really depends on what we're talking about though, because there are many different kinds of energy in an electric circuit. A capacitor stores energy in an electric field; an inductor stores energy in a magnetic field; batteries in chemical bonds. Resistors dissipate energy in the form of heat. In a perfect wire, there would be energy if the form of kinetic energy of the electrons, yes, but also in the magnetic field generated by the wire.

I know at least at the introductory college level, wires are not considered to store any energy(it's negligible). Electrons simply transfer the energy(supposedly instantaneously) from one component to the next.
 
  • #8
FireStorm000 said:
I actually remember deriving this in my AP physics class. It really depends on what we're talking about though, because there are many different kinds of energy in an electric circuit. A capacitor stores energy in an electric field; an inductor stores energy in a magnetic field; batteries in chemical bonds. Resistors dissipate energy in the form of heat. In a perfect wire, there would be energy if the form of kinetic energy of the electrons, yes, but also in the magnetic field generated by the wire.

I know at least at the introductory college level, wires are not considered to store any energy(it's negligible). Electrons simply transfer the energy(supposedly instantaneously) from one component to the next.

elegysix said:
as for the velocity of current, look up drift speed... there's a formula: I=nAQv, where v is the electron drift speed.

Electrical energy is due to the electrical field, much like gravitational potential energy.

for a given electric field E, the energy density is given by

u=[itex]\frac{\epsilon_{0}|E|^{2}}{2}[/itex]

hope this helps


thank u guys.. these answers really helped me.thanks again.
 
  • #9
Gupta:
...i thought the moving electrons collide with the nucleas of the matter which gives them vibrations and that vibration is turned into heat(for a resistor).

I am 99% sure that is not correct, but could not find a precise description within wiki...it is unlikely that nuclear activity is at the heart of heat generation...as the following excerpts indicate... Since I was looking around I thought I'd post some interesting related explanations.

[My own GUESS is that as electrons get bumped around they gain energy from the electric potential (field), then give it off randomly as they move around...so they emit some low energy photons (radiation) and we observe this as heat. Loosly bound valence electrons would neither absorb nor susbequently emit much energy...they move easily. If you look at the description below, I can visualize the "forbidden band" requiring more energy but then giving off more in return than just bumping an electron in the conduction band...]

I just checked my old physics text: it says the theory of resistance is quantum based, that classical reasoning of collisions and the like yield resistivites at least a hundred times too large. That classical reasoning involves electron collisions and the idea that free conduction electron motion is generally rapid, but that the imposed drift velocity imparts a slow uniform motion in the direction of the electric field.


Metals or metallic elements are elements with high electrical conductivity in the solid state. In each row of the periodic table the metals occur to the left of the nonmetals and thus have fewer valence electrons. The valence electrons which are present have small ionization energies, and in the solid state they are relatively free to leave one atom and move to its neighbour. These “free electrons” can move under the influence of an electric field and their motion constitutes an electric current. They are therefore responsible for the electrical conductivity of the metal.

http://en.wikipedia.org/wiki/Valence_electron#Valence_electrons_and_electrical_conductivity

Quantum mechanics states that the energy of an electron in an atom cannot be any arbitrary value. Rather, there are fixed energy levels which the electrons can occupy, and values in between these levels are impossible. The energy levels are grouped into two bands: the valence band and the conduction band (the latter is generally above the former). Electrons in the conduction band may move freely throughout the substance in the presence of an electrical field.

In insulators and semiconductors, the atoms in the substance influence each other so that between the valence band and the conduction band there exists a forbidden band of energy levels, which the electrons cannot occupy. In order for a current to flow, a relatively large amount of energy must be furnished to an electron for it to leap across this forbidden gap and into the conduction band. Thus, even large voltages can yield relatively small currents.

http://en.wikipedia.org/wiki/Electrical_resistance

TemperatureThe effect of temperature on thermal conductivity is different for metals and nonmetals. In metals conductivity is primarily due to lattice vibrations and free electron, however, free electrons play a dominant role. Therefore any increase in temperature increases the lattice vibrations but affects the movement of free electrons adversly thereby decreasing the conductivity. On the other hand conductivity in nonmetals is only due to lattice vibrations which increases with increasing temperature, and so the conductivity of nonmetals increases with increasing temperature.

Electrical conductivityIn metals, thermal conductivity approximately tracks electrical conductivity according to the Wiedemann-Franz law, as freely moving valence electrons transfer not only electric current but also heat energy. However, the general correlation between electrical and thermal conductance does not hold for other materials, due to the increased importance of phonon carriers for heat in non-metals. As shown in the table below, highly electrically conductive silver is less thermally conductive than diamond, which is an electrical insulator.

http://en.wikipedia.org/wiki/Resistance_heating#Resistance
 
Last edited:

FAQ: Electrical Energy: Is Kinetic Energy of Electrons Involved?

What is electrical energy?

Electrical energy is a form of energy that is associated with the movement of electric charge. It is the energy that is produced when electrons flow through a conductor, such as a wire, and is used to power various devices and systems.

How is electrical energy produced?

Electrical energy is produced when electrons move from a region of higher concentration to a region of lower concentration. This movement can be facilitated by a power source, such as a battery or a generator. When the electrons flow through a conductor, they transfer their energy to the device or system they are powering.

Is kinetic energy of electrons involved in electrical energy?

Yes, kinetic energy of electrons is involved in electrical energy. As the electrons move through a conductor, they have a certain amount of kinetic energy due to their movement. This kinetic energy is what is transferred to the device or system being powered, resulting in the production of electrical energy.

Can electrical energy be converted into other forms of energy?

Yes, electrical energy can be converted into other forms of energy, such as heat, light, and mechanical energy. This is done using devices like heaters, light bulbs, and motors, which convert the electrical energy into the desired form for a specific purpose.

How is electrical energy measured?

Electrical energy is measured in units of joules (J). The amount of electrical energy produced or consumed is determined by multiplying the voltage (V) by the current (I) and the amount of time (t) it is used for. This can be represented by the equation E=VIt.

Back
Top