# Is everything a resistor?

Resistance is due to collision with protons, and pretty much everything contains protons. So technically is everything a resistor? (Or at least, can anything be a resistor?)

• About no non-resistance of superconductors physics.stackexchange.com/questions/411456/… – HolgerFiedler Jul 11 '18 at 11:05
• If you're talking about physical circuit elements, then at high enough frequencies and currents, everything is simultaneously a resistor, capacitor, and inductor. – probably_someone Jul 11 '18 at 18:04
• Resistance doesn't just come from collisions with protons/nuclei. Electron-electron scattering is another mechanism that creates resistance. – dylnan Jul 12 '18 at 19:56

resistance is due to collision with protons

Actually, there are lots of materials which don't contain protons outside of atomic nuclei — e.g. steel, glass, oxygen — but all these do have resistance. Dominant factors determining resistance vary from material to material: these can be scattering of electrons/holes by motion of atomic nuclei (i.e. by phonons), by point-like defects in the crystals, etc.. Scattering by protons you mention is a very specific case of scattering by impurities (crystal defects).

technically is everything a Resistor?(or atleast, anything can be a Resistor?)

Yes, anything can be a resistor, in suitable conditions. One important property of a resistor is that it obeys Ohm's law. If you apply too high voltage to e.g. pure silicon, its conductivity will abruptly increase due to electrical breakdown. In this range of voltages the piece of material shouldn't be considered a resistor. Or if you take a piece of mercury, cool it down below 4.2 kelvins, its resistivity will become exactly zero (superconductivity), after which it can't be considered a resistor.

Similarly with other materials – in the right conditions they'll be good enough resistors, outside of these conditions they aren't.

• Does this then also mean that everything is a conductor - just depending on environment and voltage ? – Robert Riedl Jul 11 '18 at 11:26
• @RobertRiedl Apply a voltage (doesn't have to be high), and elecrtricity will move through most materials. Admittedly very slowly through some, but still. For instance, PET (the plastic) will conduct about 10^28 times lower current than copper (given the same voltage, the same geometric shape of the conductor, and more or less room temperature). Of course, if you pass the breakdown voltage (high enough to make the material basically tear apart on an atomic scale, e.g. lightning through air) then that's a different story. – Arthur Jul 11 '18 at 12:24
• "there are lots of materials which don't contain protons outside of atomic nuclei" This reads like it's saying that there are materials that have protons outside of atomic nuclei, too. I thought that protons could only escape nuclei during alpha radiation, but even then they leave as part of a helium nucleus. – JoL Jul 11 '18 at 22:04
• @JoL There are definitely materials that have protons outside of atomic nuclei. Take, for example, your typical star. It's made of a plasma of protons, electrons, and ionized nuclei. This seems to fit the definition. – probably_someone Jul 12 '18 at 0:30
• @JoL well maybe I've formulated it weirdly, but I was thinking about hydrogen (protium), whose nucleus is proton itself, not just contains protons as do all the other nuclei. If you suggest a better wording, I'll fix the answer. – Ruslan Jul 12 '18 at 4:47

Well, almost everything exhibits some form of resistance, with the exception being superconductors which have zero resistance. So yes, you're correct.

• I was also told by my physics teacher that water was incompressible. Which is obviously technically incorrect, but compared to air, its certainly very hard to compress. So how "Zero" is the zero resistance of super conductors? Its certainly very very low. But If I started a current of some kind flowing in a superconductor, could I literally come back millions of years later and it would still be flowing? – Chris Becke Jul 11 '18 at 11:19
• @ChrisBecke theoretically yes, the principle is called "persistent current", there is a wikipediapage on it. I'm not sure if i'm allowed to link to it here, but you can google it and it should be somewhere around the top. Citation from Wikipedia : "The persistent current was first identified by Onnes, and attempts to set a lower bound on their duration have reached values of over 100,000 years", and they have a source to it so if you're interested you should look it up! – DakkVader Jul 11 '18 at 11:25
• @DakkVader sure you're allowed to link to Wikipedia, or any other site. Just use the [label](URL) Markdown syntax. In fact you positively should link to a source if you quote text! – leftaroundabout Jul 11 '18 at 11:36
• @ChrisBecke actually zero. It's one of those quantum things. A superconductor (under the conditions where it's superconductive) can't dissipate electronic energy without entering a forbidden state, so it just... doesn't. – hobbs Jul 11 '18 at 19:37
• @hobbs In ideal situation superconductor would conduct forever, but nothing's ideal. Otherwise it would be perpetuum mobile. Even neutrinos and gravity waves can dissipate energy. – Mithoron Jul 11 '18 at 22:06

The definition of what a resistor is is not always clear. As an EE, I would recommend phrasing it "Everything has a resistance. Not everything is a resistor." Through every object, if there is a voltage difference from one side to the other, current will flow through it, however minuscule.

I would not call them resistors because it is more useful to reserve the term "resistor" for a component which I use in a way which is generally consistent with Ohm's Law. For example, a capacitor has resistance. Electrons will eventually move from one side of a capacitor to another, given a sufficient voltage across the capacitor. I can calculate it's resistance. However, the behavior of a capacitor is generally very far from that of a resistor, so thinking of that capacitor as a resistor would only confuse me unless I am specifically looking at the leakage currents through a circuit.

Likewise, any high voltage electrician will tell you that everything conducts: air, rubber, plastic, glass, sulfur-hexafloride. Everything conducts. Not everything is considered to be a conductor. Those insulators holding up the power lines above our heads have one job: to not be a conductor. That being said, they do indeed conduct some current. They are just designed to do it so minimally that they can be used as an insulator as well.

No not everything is a resistor. A resistor is a device with two terminals for which voltage is proportional to current. This cannot be said of insulators, diodes, transistors and many other devices.

• Perhaps the question should have been worded, "does everything have resistance" but as it stands, insulators, diodes, transistors and nearly every other component you could name does indeed act as a resistor in some capacity or another. – TheEnvironmentalist Jul 11 '18 at 10:13
• It could have been worded "does everything have a resistivity", which refers to the micro structure and material properties rather than bulk behavior. – ggcg Jul 11 '18 at 11:07
• @my2cts, You answer seems to imply that insulators are good conductors since they do not resist the flow of current. You may want to reword the answer. If you feel that the OP was unclear (which is the case) then put it back on them to clarify. All of the devices you list "resist" the flow of current in some sense of the term and in some, if not all, cases. – ggcg Jul 11 '18 at 11:09
• For most of the common materials from which insulators are built (e.g. plastic, glass, ceramics) the current is perfectly well proportional to the voltage; it's just that the specific conductivity of these materials is very low so that the resulting currents are very low as well; in most cases they are hopefully negligible. (But they do exist, and they do follow Ohm's Law, within reasonable voltage limits.) – Peter A. Schneider Jul 12 '18 at 13:26

In electrical engineering, "resistor" means two things:

• A theoretical two terminal device with a voltage drop equal to the current times a value "R" which is the resistance of the resistor.
• The physical devices sold to act as closely as possible to the theoretical abstraction above (also the most commonly used items in circuit design).

So a diode, for example will look nothing like a resistor. It will have two terminals, but voltage as a function of current will be exponential instead of linear.

Another big issue from a physics standpoint is that voltage and current are mostly defined on a macroscopic scale (although I assume that engineers speak of voltage and current even with the smallest produced chips). I doubt the concept is well defined on the atomic level.

So while "resistor" may sound like a good description of something between "conductor" and "insulator", be aware that "resistor" implies a linear relation across many voltage and current levels. I'd say no. "Everything" is just too broad and "resistor" far too narrow. Saying "everything is a resistor" is as equally true (and false) as saying "everything is an inductor" or "everything is a capacitor". It completely ignores the meaning of "resistor".

• What's the problem with voltage and current definition on the microscopic level? – Dmitry Grigoryev Jul 13 '18 at 6:31

It appears that you have some terminology misunderstanding.
Resistance is a property exhibited by all materials, but it is due to the electrons, NOT the protons (by definition).
A resistor is a particular electric component that exhibits resistance.

With these definitions in place, it becomes obvious that everything is not a resistor, but anything that offers opposition to electron flow, has resistance.

A good number of metals and some ceramics are superconductors at low temperature. Donut-shaped superconductors have maintained a flow of current for years. These experiments/demonstrations prove that not all materials exhibit electrical resistance. To answer the question: no, not all materials are resistors.

An argument might be made that some superconductors cannot be resistors (or exhibit resistivity) below their transition temperatures in the absence of external forces. The electrons are in a "condensed" state and cannot be scattered, the cause of resistance for normal conductors.

Resistance is related to atomic and molecular structure and not directly to protons. Low resistance materials like metals have degenerate electrons, higher resistance materials the opposite. For metals, resistance is lowest for highly regular molecular/crystal structures. It is reduced as temperature is lowered because electron scattering is reduced.

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