# How does copper create electrical flow? **URL:** \ **Category:** Factual Questions\ **Created:** [October 9, 2013, 2:17pm UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773 "2013-10-09T14:17:33Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [October 9, 2013, 2:17pm UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/1 "2013-10-09T14:17:33Z")
This seems like such a stupid question, especially from someone with 30+ years of electronic and electromechanical design experience, but it struck me the other day that I do not know why copper and similar nonferrous metals generate electrical flow when they are moved through a magnetic field. Shouldn’t generator (and conversely, motor) windings have to be a magnetically susceptible material - iron-based - in order to interact with the magnetic or electromagnetic fields and generate electron/electricity/current flow? If copper and silver and gold are nonmagnetic, how do they interact with the magnetic field to produce current? Do materials like plastic interact with the magnetic field in the same way, but produce no current flow because they are electrically nonconductive? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [October 9, 2013, 2:22pm UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/2 "2013-10-09T14:22:35Z")
The magnetic field is acting on the “sea of electrons” in a conductor - those electrons that are prroly bound, and free to move around. Materials that are magnetic (ferromagnetic) have crystalline grains that are magnetic dipoles due (mostly) to the alignment of electron spins. ---
**Author:** ![chrisk](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@chrisk](https://boards.straightdope.com/u/chrisk)\ **Post date:** [October 9, 2013, 2:28pm UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/3 "2013-10-09T14:28:12Z")
All electrons are charged particles and will interact with electromagnetic fields. All metals that are electrically conductive allow electrons to move freely from atom to atom, and so they’ll produce a current flow when moved through a magnetic field. I’m a little fuzzy on the distinction between copper and iron in terms of magnetism, actually, but I believe it has to do with the way large numbers of iron atoms can arrange themselves so as to induce magnetic fields without an external source of current. That’s what’s meant by ‘ferromagnetic’ IIRC. But the fact that copper doesn’t have this property doesn’t mean that its electrons don’t interact with electromagnetic field. I’m pretty sure, for instance, that you could create a strong electromagnet out of only copper, insulating materials, and a battery; with no iron or other traditionally magnetic metals at all. On edit: Thanks, beowulff; the crystalline grains/magnetic dipoles stuff fills in some of what I was fuzzy on. (Did it really take me six minutes to write that answer?) ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [October 9, 2013, 2:29pm UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/4 "2013-10-09T14:29:45Z")
the conductivity of a metal is from the nature of its metallic bond. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [October 9, 2013, 2:36pm UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/5 "2013-10-09T14:36:37Z")
[Lorentz force](http://en.wikipedia.org/wiki/Lorentz_force). Force on a moving charge is q **v** cross **B** where q is charge, **v** is velocity and **B** is magnetic field. For a wire, the electrons have negative charge, and the nuclei have positive charge, so the electrons are pushed in an one direction, and the copper nuclei in the other, causing current flow. Generally, something is holding the wire, so it just transfers the force on it, and the wire is much more massive than the electrons anyway. But the (conduction) electrons are free to move, causing current. ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [October 9, 2013, 3:02pm UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/6 "2013-10-09T15:02:22Z")
I think, firstly, you can’t be thinking in terms of electricity and magnetism. They are inseparable; where there is one, there is the other. As to how they generate EMF, isn’t that how an inductor works? It resists changes in magnetic field by creating its own. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [October 9, 2013, 3:14pm UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/7 "2013-10-09T15:14:00Z")
> [@Amateur\_Barbarian](#): > > Do materials like plastic interact with the magnetic field in the same way, but produce no current flow because they are electrically nonconductive? Forgot to answer this: Yes. They have no conduction electrons, only electrons that are bound to individual molecules. The electrons will still be pushed one direction, and the nuclei the other, but the molecule holds onto all its electrons, so you would just get a small electric dipole moment, no large current flow. For conductors, it’s only the outer, valence, electrons that conduct. The rest are tightly bound to the nuclei. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 9, 2013, 3:16pm UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/8 "2013-10-09T15:16:35Z")
Electromagnetic induction is by far the simpler effect; it’s ferromagnetism that’s the complicated one. ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [October 9, 2013, 3:30pm UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/9 "2013-10-09T15:30:37Z")
I forgot to answer this too. > [@Amateur\_Barbarian](#): > > Do materials like plastic interact with the magnetic field in the same way, but produce no current flow because they are electrically nonconductive? I think, yes, the magnetic field has the same effect on the charge carriers in insulators, but since the charge carriers are tightly bound (usually to the nuclei), they can’t move and there’s no current. But they can oscillate. And there’s a resonant frequency. If you hit them with the resonant frequency, they’ll oscillate more and more and not eventually move, but the material gets hot. That’s how microwaves work. Lots of materials don’t seem to absorb microwaves, but that’s because cooking microwaves aren’t tuned to their frequency. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 9, 2013, 5:14pm UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/10 "2013-10-09T17:14:48Z")
Microwaves aren’t particularly “tuned”, though. In normal operation, you’re mostly shaking up water molecules, and they’ll respond to a wide range of frequencies. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [October 9, 2013, 11:52pm UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/11 "2013-10-09T23:52:40Z")
Plastics and other “non-conductive” materials can build up one hell of a static electric charge (Basically a sea of negative electrons waiting to discharge into a material that has a likewise unbalanced and opposite charge. PVC is great for building up static, but think Balloon on hair and stuck to wall… or even more visceral, wool socks on carpet then touching finger to doorknob… zzztt.). ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [October 9, 2013, 11:56pm UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/12 "2013-10-09T23:56:24Z")
The electrical property of resistance and conductivity are in play. Copper was chosen because it has low resistance compared to other metals. Aluminum was tried in the 1970’s but it didn’t hold up well in actual use. Gold and Silver are the best conductors but too expensive for wiring. > **[Electrical resistivity and conductivity](https://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity)** > > Electrical resistivity (also called volume resistivity or specific electrical resistance) is a fundamental specific property of a material that measures its electrical resistance or how strongly it resists electric current. A low resistivity indicates a material that readily allows electric current. Resistivity is commonly represented by the Greek letter ρ (rho). The SI unit of electrical resistivity is the ohm-metre (Ω⋅m). For example, if a 1 m3 solid cube of material has sheet contact Electr... > [@](#): > > Electrical resistivity (also known as resistivity, specific electrical resistance, or volume resistivity) quantifies how strongly a given material opposes the flow of electric current. A low resistivity indicates a material that readily allows the movement of electric charge. Resistivity is commonly represented by the Greek letter ρ (rho). The SI unit of electrical resistivity is the ohm⋅metre (Ω⋅m)[ > [@](#): > > Electrical conductivity or specific conductance is the reciprocal of electrical resistivity, and measures a material’s ability to conduct an electric current. It is commonly represented by the Greek letter σ (sigma), but κ (kappa) (especially in electrical engineering) or γ (gamma) are also occasionally used. ---
**Author:** ![Glazer](https://avatars.discourse-cdn.com/v4/letter/g/a88e57/32.png) [@Glazer](https://boards.straightdope.com/u/Glazer)\ **Post date:** [October 10, 2013, 12:46am UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/13 "2013-10-10T00:46:33Z")
Everything reacts with electromagnetic fields. Otherwise you’d fall right through your chair. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [October 10, 2013, 1:29am UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/14 "2013-10-10T01:29:11Z")
> [@Glazer](#): > > Everything reacts with electromagnetic fields. Otherwise you’d fall right through your chair. [Neutrinos don’t. Therefore, 65 billion (6.5×10^10) solar neutrinos per second pass through every square centimeter perpendicular to the direction of the Sun in the region of the Earth.](http://arxiv.org/abs/astro-ph/0412440) And yet [we have strong evidence they have mass](http://arxiv.org/abs/hep-ex/0412032). [Here is a perhaps more readable description of why we think that from Super-Kamiokande, the observatory which discovered the evidence.](http://www.ps.uci.edu/~superk/oscillation.html) So, yes, respecting electromagnetism is necessary but not sufficient for being able to sit in a chair. Keep that in mind the next time you decide what kind of matter you want to be made out of. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [October 10, 2013, 1:43am UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/15 "2013-10-10T01:43:35Z")
[Here’s a _much_ more readable citation for the first statement.](http://zebu.uoregon.edu/~soper/Sun/solarneutrinos.html) This claims 6.5 × 10^14 m^‒2 s^‒1 as the solar neutrino flux through the regions of Earth facing directly towards and away from the Sun, which is exactly the same value as my other cite if you do unit conversion. Isn’t metric fun? ---
**Author:** ![Glazer](https://avatars.discourse-cdn.com/v4/letter/g/a88e57/32.png) [@Glazer](https://boards.straightdope.com/u/Glazer)\ **Post date:** [October 10, 2013, 1:48am UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/16 "2013-10-10T01:48:01Z")
I had a neutrino chair once, but it fell through the floor. ---
**Author:** ![excavating\_for\_a\_mind](https://avatars.discourse-cdn.com/v4/letter/e/e8c25b/32.png) [@excavating\_for\_a\_mind](https://boards.straightdope.com/u/excavating_for_a_mind)\ **Post date:** [October 10, 2013, 2:28am UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/17 "2013-10-10T02:28:17Z")
> [@aceplace57](#): > > The electrical property of resistance and conductivity are in play. Copper was chosen because it has low resistance compared to other metals. Aluminum was tried in the 1970’s but it didn’t hold up well in actual use. Gold and Silver are the best conductors but too expensive for wiring. While the above is true, it isn’t entirely true. On a percentage basis, nearly all electricity produced travels through aluminum conductors. High tension transmission wires: Aluminum. Buss bars in electrical sub-stations: Aluminum. Yes, Aluminum was tried as residential wiring and failed (mainly because of improper installation; the electricians tried to treat it exactly the same as copper). In the big picture, the reason it failed is unimportant, since failure usually resulted in fire, but there is a reason aluminum is so widely used for conducting electricity Aluminum is lighter than copper, so in for long runs suspended by towers, using aluminum lowers the weight load the towers have to support, so the towers don’t have to be as big. Copper, while it is not ferromagnetic, is paramagnetic. Simply put, copper cannot be magnetized like iron, but it does respond to a magnetic field in a way that aluminum does not. The result is that a copper wire produces a hysteresis in the phase angle between current and voltage in AC transmission that aluminum does not. This hysteresis creates a transmission load that is absent when aluminum wire is used. Now, it is correct that the aluminum has higher resistivity than copper, but by using a larger diameter cable, the resistivity per unit length of an aluminum cable can be made to be the same as a copper cable, but because the aluminum cable will not suffer the hysteresis seen with the copper cable, the larger aluminum cable will actually have lower line losses than the copper cable. And, it’s cheaper. Now, with residential wiring, the hysteresis losses are negligible and the fact that poorly installed aluminum wiring can burn your house down makes copper the material of choice. ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [October 10, 2013, 2:49am UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/18 "2013-10-10T02:49:24Z")
> [@Chronos](#): > > Microwaves aren’t particularly “tuned”, though. In normal operation, you’re mostly shaking up water molecules, and they’ll respond to a wide range of frequencies. They’re not finely tuned, but the shape of the magnetron only encourages certain frequencies, which is how you get standing waves (cold spots) and other effects. They’re certainly not “white” RF. ---
**Author:** ![Jeff\_Lichtman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jeff_lichtman/32/1531_2.png) [@Jeff\_Lichtman](https://boards.straightdope.com/u/Jeff_Lichtman)\ **Post date:** [October 10, 2013, 8:40am UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/19 "2013-10-10T08:40:03Z")
Getting back to the OP: it has nothing to do with whether the wire itself is made of a “magnetic” material like iron. The attraction of iron (and a few other metals) to magnets and the ability to make permanent magnets of them is a different phenomenon called “ferromagnetism.” A change in a magnetic field creates an electric field (and vice versa). So when you move a magnet past a point in space, the magnetic field around that point changes, creating an electric field around the same point. This electric field puts forces on charged particles like electrons. In conductive materials (like metals), electrons can move from molecule to molecule pretty easily, so an electric field can cause a flow of electrons in one direction or another. This is how a generator works: a moving magnet near a wire creates an electric field that causes electrons to flow along the wire. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [October 10, 2013, 10:44am UTC](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773/20 "2013-10-10T10:44:14Z")
> [@excavating\_for\_a\_mind](#): > > …poorly installed aluminum wiring can burn your house down makes copper the material of choice. Homes with aluminum wiring that were built before 1972 were most problematic, as AA-1350 series aluminum wire was used. After 1972 the 8000-series aluminum wire was introduced, which did not have the same problems as the older AA-1350 alloy; this new alloy had similar tensile strength and CTE as copper. But by then aluminum wiring had such a black eye that no one would use the new stuff. [Next page](https://boards.straightdope.com/t/how-does-copper-create-electrical-flow/670773.md?page=2)