# Why is there no net current in a wire without a voltage applied?

Atoms of materials with loosely bound outermost electrons constantly exchange charges between each other over time, and these materials are called conductors. Now, the conducting process is different from the one often described in the electrical engineering textbooks.

This implies that in order for current to flow in the circuit, an electron has to move from one lead all the way to the other, which is simply not true. Reality is something like this:

The electron at the far left coming from the negative lead of a battery, for example, is then colliding at the nearest atom and because of its acceleration it's knocking out the electron which is revolving at this shell level. The knocked electron is heading to its closest atom and in turn it's doing the same, knocking out an electron which creates a chain reaction. So, basically, electrons move just a little bit, but the overall outcome is virtually instantaneous.

What I don't understand is if we take a regular conductive wire WITHOUT applied voltage on it, electrons still constantly bounce from atom to atom which means that literally there is "an electron flow" in the wire, but if we connect the wire to a LED diode nothing would happen. So, what I am really asking is how differs "an electron flow WITH applied voltage" from "an electron flow WITHOUT applied voltage" in a wire.

• Voltage is a difference in potential. Thus, electric field. Charged particles tend to move to opposite terminals. In this case, electrons want to move across the wire to a + terminal. If no voltage is applied, there is no potential difference and no electric filed, so electrons are not much effected: they move randomly with no net flow. Dec 30, 2016 at 16:30
• Lady, I suggest you to read up something about the metallic bond. Electrons are not 'knocking out each other'. Not even close. Perhaps the sea of nearly free electrons in a grid of positive ions is a more apt pictorial model at this level. Then you have to ask yourself: why there has to be a preferable direction for electron flow when there is no field applied? - Reading suggestion: "Kip, Fundamentals of electricity and magnetism, 2e" Dec 30, 2016 at 16:37
• You're talking about the difference between current and drift velocity. I suggest searching on that term Dec 30, 2016 at 16:43
• Thank you so much, guys, for quick reaction, I m sorry that I messed up with the "electron to electron colliding" thing, also, I m sorry that I asked the question in the wrong section, I just thought that Electrical Engineering was the place to ask, anyhow, Wish you much success happy holidays Dec 30, 2016 at 17:34
• @SredniVashtar you didn't intend it, but addressing a woman as "Lady..." comes across as rude. Generally you just use their name.
– smci
Dec 31, 2016 at 3:31

Statistically, there are as many electrons moving in one direction as there are in the 180º opposite so there is effectively no net current. What we know as "current" is the movement of more electrons in one direction than all the others (1D, 2D or 3D through a piece of metal). That's how you can have "tons of free electrons" but no net currents flowing or measurable.

The random agitation of those electrons has a name: thermal noise. This agitation is proportional to temperature so you get more of it as you heat things up. However, the average motion is always zero so you can never do any useful "work" or equivalently extract usable energy from the process.

This is in agreement with the laws of thermodynamics.

• The average motion may be zero, but that does not mean that you can't do useful work or extract useful work from the process. Only when the temperature is constant everywhere does it become impossible to extract energy from thermal noise. Dec 31, 2016 at 17:28
• And then there were superconductors. Dec 31, 2016 at 23:47

Short answer: some textbooks are infected with a misconception, the idea that electrons always orbit the individual metal atoms. Nope. They'll also tell you that electrons only jump between atoms when a voltage is applied along the wires. Wrong.

In metals, the outer electron(s) of each metal atom have left their original atom. This happens when the metal is first formed. If electrons kept sticking to each atom, then the metal would be an insulator, and at low values of current, the ohms wouldn't be constant. In reality, the outer or "conduction band" electrons are orbiting among all the metal atoms, all the time. A metal wire resembles a kind of "solidified plasma." Metals are weird.

Physicists call the metal's mobile electron-population by the name "electron sea" or "ocean of charge." In chemistry it's called the "metallic bond."

From a non-quantum viewpoint, we can view metal objects as being like containers filled with an "electric fluid," Ben Franklin-style! The metal's electrons are jittering around at high speed, wandering all around, much like the molecules of gas inside a hose. But this electron-motion is in random directions. It's a storehouse for thermal energy, but it has no single direction, so it's not "wind;" not electric current. For every electron going one way, there's another going backwards.

Therefore, an actual DC electric current in a metal is a slow average drift of this electron cloud. Individual electrons don't move slow of course. Instead they wander around at nearly the speed of light all the time. But during a DC current, their average wandering path has a tiny DC drift superimposed. Earth's atmosphere does the same: each molecule is moving at nearly the speed of sound, even in dead still conditions; no wind. We regard the wandering as "thermal," as Brownian Motion. Same with individual electrons in a metal.

A correct animation of atoms/electrons of metals would depict the electrons jumping in both directions for zero current. Or, show them wiggling back and forth across several atoms, with random motion during zero amperes. (Or, show the inside of the wire looking like 'television snow,' like flickering white-noise.) Then, during a DC current, the entire pattern of electrons will slowly slide along as a unit. The higher the amperes, the faster the flow. The "liquid white-noise" moves slow, like water in a pipe, but the individual particles never remain still.

Note that this picture DOES NOT APPLY TO ALL CONDUCTORS. It only applies to solid metals (the most common form of conductor used in electrical engineering), but not to salt water, acids, ground currents, human tissue/nerves, liquid metals, moving metals, plasma, sparks, etc. Electricity isn't electrons, that's why engineers and scientists use the "Conventional Current" which applies to all types of conductors. Electron-flow within metals is a special case of electric currents in general.

PS
Note that electrons aren't invisible! (In fact, electrons are about the only things that are visible.) So, whenever we look at a bare wire, we're seeing its electron-sea. The mobile electrons are extreme reflectors of EM waves. The "metallic" look of a metal surface is our view of the free electrons. So, electrons are like a silvery fluid. During electric currents in a metal, it's the silvery stuff that flows along. But there's no dirt or bubbles in this flow, so although we can see the "fluid," we can't see its motion. (Heh, even if we could see something moving, the charge-drift would be too slow to notice; like the minute hand on a clock!)

• But why is that so, why do studying materials that are supposed to ensure accurate expanations turn out providing false conclusions about a certain topic . However, what is even more dangerous is the fact that they delude the reader of imaginary understanding? As one of the people earlier today pointed out my ignorace regarding the statement I made about "electron to electron collision", but I didn't come up with it on my own, though, instead I read it in a book Dec 31, 2016 at 4:22
• @Nina Vladimirova In the USA, textbooks are not reviewed by scientists and engineers, they are only reviewed by local "textbook committees," non-experts. The purchases of the largest state (Texas) dominate. Result: corruption of all textbooks. No checks/balances! Also, slow errors cannot be repaired, because publishers ignore teachers' complaints because ALL TEXTBOOKS have identical error. (Who are you to say you are correct, when all textbooks say different?) See textbookleague.org/103feyn.htm & textbookleague.org/ttlindex.htm and my amasci.com/miscon [Edited] Dec 31, 2016 at 5:48
• All understanding is imaginary.
– user56384
Dec 31, 2016 at 13:39
• @wbeaty. Great answer. Dec 31, 2016 at 23:50
• @wbeaty Thank you, sir, May I ask you for any suggestions regarding study materials(textbooks) with deep particularity and yet accurat explanations about electronics. Starting from the very basics, book/books which is going to give me strong foundations and prepare me for some advanced topics? Jan 2, 2017 at 17:11

If the wire is a superconductor, current can indeed flow without voltage.

• Well, it can drop without a voltage dorp. You still need something to get the current flowing in the first place. A superconductor with no current and no voltage will not spontaneously exhibit a consistent current flow (i.e., lightening up a diode as per the question).
– AnoE
Dec 30, 2016 at 21:13
• @AnoE: Have you ever seen a superconductor in a magnetic field? Plenty of current, still no voltage. Dec 31, 2016 at 23:46
• "You still need something to get the current flowing in the first place." and back to the question, a superconductor certainly does not count as "regular conductive wire".
– AnoE
Dec 31, 2016 at 23:56

Electrons without voltage are simply like independent people liking at some random city. They happily move freely but they aren't part of any movement. They are individual that don't matter.

Now all of a sudden a foreign party establishes the rule. That makes electrons march to the establishment of the foreign party(Not the conventional current) in revolt , rebel etc etc. They are the part of the movement and that is called Current.

Current requires electrons in the conduction band to flow, and without voltage (or pressure as an flow analogy), there is no energy to excite the electrons into the conduction band. Resistance is always present due to atomic properties, and the voltage drop must be the total voltage as resistance becomes essentially infinite as the valence shells in metals are much different than conduction bands in that they are bound to the lattice structure of the metal. They require excitation and a gradient to break their bond with the valence she'll. Valence electrons can interact but they are not uniformly directional and are not free flowing like they would be if excited into the conduction band. This is of course for simple conductive metals.

From your question, it is clear that you don't know the distinction between random electron movement and directional electron movement. Random electron movement is not current. Directional electron movement is.
It is the voltage that gives direction to the electrons, thus causing directional electron flow - the "electron current."

Your assertion that "an electron has to move from one lead... to the other, is simply not true," is wrong. The fact is that for every electron that "enters" into the wire, another electron must "exit" from the other end. If this doesn't happen, then you don't have current flow! This is exactly why "nothing happens when you connect the LED to the wire" with no voltage applied.

We are told to not bother because there is more physics in it and less practical importance.

In physics the wire is not a dead short but has resistance, capacitance and inductance.When you apply voltage in a wire many thinks happens.

When there is no voltage applied there are not enought electrons jumping from atom to atom to make the LED light.

A physisist could answer that better than an EE. There is a physics section in the stack exchange.

• Not a very useful answer ... Dec 30, 2016 at 18:21
• @Tedi Thank you, I found it, appreciate your answer. Dec 30, 2016 at 20:45
• Sorry I did my best.
– Tedi
Dec 30, 2016 at 23:14