# Reversing the Polarity **URL:** \ **Category:** Factual Questions\ **Created:** [September 4, 2017, 3:11am UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450 "2017-09-04T03:11:44Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [September 4, 2017, 2:11pm UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/21 "2017-09-04T14:11:19Z")
You can’t leave us in suspense like that. Did it work, Man?? Did it work!!??!! See also: [xkcd: Wisdom of the Ancients](https://xkcd.com/979/)😃 ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [September 4, 2017, 2:12pm UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/22 "2017-09-04T14:12:42Z")
I like to sometimes put cat food in the dog food bowl and dog food in the cat food bowl … the dog figures out my little dodge pretty quick but boy-oh-boy do the cats get reversed … ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [September 4, 2017, 2:14pm UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/23 "2017-09-04T14:14:31Z")
If you reverse the polarity of your microwave oven you can make ice cubes in 30 seconds. ---
**Author:** ![What\_Exit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/what_exit/32/10652_2.png) [@What\_Exit](https://boards.straightdope.com/u/What_Exit)\ **Post date:** [September 4, 2017, 2:16pm UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/24 "2017-09-04T14:16:08Z")
> [@LSLGuy](#): > > You can’t leave us in suspense like that. Did it work, Man?? Did it work!!??!! > > See also: [xkcd: Wisdom of the Ancients](https://xkcd.com/979/)😃 Sorry about that, **it did work**. If you like and I remember, I’ll include the model number of the device in question tomorrow in case some other poor soul has to maintain a twinax printer or terminal in this modern age. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [September 4, 2017, 2:26pm UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/25 "2017-09-04T14:26:14Z")
> [@jz78817](#): > > That is only true for permanent magnet DC motors. Series-wound motors will run the same direction regardless of polarity There are many exceptions to your notion. Duck-Duck’s first hit @ [http://www.ecmweb.com/content/determining-dc-motor-rotation-direction](http://www.ecmweb.com/content/determining-dc-motor-rotation-direction) provides some info. Essentially, reversing field polarity on series motors reverses their rotation. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [September 4, 2017, 2:27pm UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/26 "2017-09-04T14:27:48Z")
> [@Enola\_Straight](#): > > When recording “The Joshua Tree”, U2 came across a newly-invented instrument called the Infinite Guitar: by re-jiggering a set of pick-ups to act as a speaker instead of a microphone, a feed-back loop was created, providing infinite sustain. True but this is not reversing the polarity. I have a 1970s ES-335-TDC and put a polarity-reverse switch on one of the pickups. I didn’t really know what I was doing but when I play the reversed-polarity turned on, and both pickups turned on, I get a thin twangy tone very uncharacteristic of Gibsons, and probably as close as you will get to a Strat on an otherwise stock ES-335. I don’t really know what is happening electronically to cause the effect. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [September 4, 2017, 3:36pm UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/27 "2017-09-04T15:36:03Z")
While this is just a hobby I screw around in my garage doing and have very little experience. Reverse Polarity (or reversing the polarity) is very common in welding. When you see someone welding and they have a gun or stick in their hand and a clamp on the metal, before starting they first choose which thing is + and which is -. I’ve read a lot of anecdotes about people practicing for weeks or months with their welders and getting nowhere and finally having a friend help them out only to find out they have the polarity backwards for the type of rod/wire they’re using. They either didn’t know it was an option, read the chart wrong or changed it at some point and never changed it back. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [September 4, 2017, 3:52pm UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/28 "2017-09-04T15:52:30Z")
Troubleshooting CAT5 data connections, it’s amazing how many times merely swapping wires one and two fixed the problem. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [September 4, 2017, 3:56pm UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/29 "2017-09-04T15:56:28Z")
The only examples I can come up with are this young lady’s pole [reversal](http://ipole.tv/wp-content/uploads/2009/01/cimg9094-2.jpg) and the historical division, elimination, and restoration of [Poland](http://kehilalinks.jewishgen.org/ostropol/_images/tale_two_shtetls_echenbergs/20thCenturyPoland.jpg) thru the 20th century. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [September 4, 2017, 3:58pm UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/30 "2017-09-04T15:58:51Z")
> [@Chronos](#): > > …That said, if you reverse the polarity on an incandescent light bulb, it’ll produce anti-photons. The joke, in case anyone didn’t realize, is that photons are their own antiparticle. Which does relate to the interesting point that there is a remote possibility that isolated distant galaxies might be made of antimatter. The light would look the same. > **[Are there antimatter galaxies?](https://phys.org/news/2016-06-antimatter-galaxies.html)** > > One of the biggest mysteries in astronomy is the question, where did all the antimatter go? Shortly after the Big Bang, there were almost equal amounts of matter and antimatter. I say almost, because there was a tiny bit more matter, really. And... ---
**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:** [September 4, 2017, 4:29pm UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/31 "2017-09-04T16:29:13Z")
I learned a Gilligan’s Island that [a radio receiver can be turned into a transmitter by simply reversing the transistors](http://boards.straightdope.com/sdmb/showthread.php?t=135255). 🙂 ---
**Author:** ![snfaulkner](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/snfaulkner/32/433_2.png) [@snfaulkner](https://boards.straightdope.com/u/snfaulkner)\ **Post date:** [September 4, 2017, 9:25pm UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/32 "2017-09-04T21:25:16Z")
Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light. Total protonic reversal. ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [September 5, 2017, 12:19am UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/33 "2017-09-05T00:19:25Z")
> [@snfaulkner](#): > > Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light. > > Total protonic reversal. tell 'em about the Twinkie. ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [September 5, 2017, 1:46am UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/34 "2017-09-05T01:46:02Z")
> [@Chronos](#): > > The only time reversing the polarity solves a problem is when the problem was that you had the wrong polarity to begin with. If the Enterprise was working fine before Scotty got his hands on it, then reversing the polarity won’t help. > > That said, if you reverse the polarity on an incandescent light bulb, it’ll produce anti-photons. > > (I can’t remember who I stole that from, but it was someone here) Actually, that was me. > [@Reversing the Polarity](https://boards.straightdope.com/t/reversing-the-polarity/123345/29): > > I reversed the polarity on my desk lamp by pulling out the plug and putting the plug back in upside-down. > > Now the light bulb emits ANTI-photons! > :eek: [https://boards.straightdope.com/sdmb/showthread.php?t=130145&highlight=polarity](https://boards.straightdope.com/sdmb/showthread.php?t=130145&highlight=polarity) ---
**Author:** ![Sparky812](https://avatars.discourse-cdn.com/v4/letter/s/eb9ed0/32.png) [@Sparky812](https://boards.straightdope.com/u/Sparky812)\ **Post date:** [September 5, 2017, 2:06am UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/35 "2017-09-05T02:06:17Z")
Photovoltaic solar panels will heat up when their polarity is reversed. This proves to be useful when snow/ice has accumulated and there’s not enough sunlight to melt it off. ---
**Author:** ![Yllaria](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yllaria/32/3452_2.png) [@Yllaria](https://boards.straightdope.com/u/Yllaria)\ **Post date:** [September 5, 2017, 2:35am UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/36 "2017-09-05T02:35:03Z")
> [@Riemann](#): > > I don’t know, but it wasn’t just Star Trek. Using his sonic screwdriver to reverse the polarity has long been SOP for Doctor Who. The third doctor often reversed the polarity of the neutron flow. I still appreciate that wink. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [September 5, 2017, 2:40am UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/37 "2017-09-05T02:40:45Z")
You can certainly reverse the polarity of an AC signal, however it is just equivalent to a 108 degree phase shift. This can be important. > [@CookingWithGas](#): > > True but this is not reversing the polarity. True, although in a feedback system phase matters. > [@](#): > > I have a 1970s ES-335-TDC and put a polarity-reverse switch on one of the pickups. I didn’t really know what I was doing but when I play the reversed-polarity turned on, and both pickups turned on, I get a thin twangy tone very uncharacteristic of Gibsons, and probably as close as you will get to a Strat on an otherwise stock ES-335. I don’t really know what is happening electronically to cause the effect. Where it comes from is the different locations of the two pickups. If the strings next to each pickup had identical vibration, and the pickups were identical in design, you would get close to zero signal. However even with identical pickups, the harmonics on the string each pickup will see are different. The fundamental will be very similar at each pickup, and will largely cancel out, but the harmonics won’t be the same and, in general, won’t cancel out, or will variously cancel and not depending upon the note fretted and the location of the two pickups (especially the distance between them.) So you minimally lose the fundamental out of the note, and get an alteration of the harmonic structure as well. Loss of the fundamental alone will get you a thin sound, and the interactions with the harmonics probably adds to the twangy nature. ---
**Author:** ![LH75](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lh75/32/4438_2.png) [@LH75](https://boards.straightdope.com/u/LH75)\ **Post date:** [September 5, 2017, 11:22am UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/38 "2017-09-05T11:22:10Z")
Many of the 24vdc components of fire alarm systems will not survive a reversal of polarity. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [September 5, 2017, 11:47am UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/39 "2017-09-05T11:47:35Z")
Here’s an example from my own grad student career. Take a cubically-cut alkali halide crystal (like common table salt, sodium chloride NaCl, although I usually worked with potassium chloride, KCl) about a cm or so long. Place it between a couple of platinum electrodes (or at last platinum-faced electrodes) in a high-temperature oven. Heat it up until it’s not quite to the melting point – about 100 degrees (F) shy of it. Now apply a voltage of about 1000 volts across the crystal. You will inject electrons into the crystal that will form the defect centers called “color centers” by electrolysis. It looks as if you are pouring ink into water. The color-center-rich region has a definite boundary, and the color is deep and beautiful. In NaCl (and many other alkali halides) the color centers are a deep blue, but in KCl they form a purple “cloud”. If you rig the demonstration up in a tubular over, you can put a light source at one end and a lens at the other and project the process onto a screen. It’s a freakin’ gorgeous demonstration. Here’s the “Reverse the Polarity” part – if you now reverse the polarity of the electrodes, so that what was positive becomes negative and vice versa, you can make that “cloud” of color centers appear to go “back into” the electrode. The blue or purple color appears to completely reverse itself, as if it’s getting sucked into the electrode. This, too, can be projected. What is interesting – and the reason that I did the experiment – is that in certain cases (alkali halide crystals doped with other intentional impurities) when you reverse the electrode polarity and withdraw the color center cloud, what remains behind is not the perfectly clear crystal, but a host of other defect centers that _don’t_ go away with reversing the polarity. These were what I wanted to create, hoping that they’d have certain desirable properties, like stability. well, they _were_ very stable, but they didn’t do the other thing I’d wanted. Oh, well, back to the drawing board. Another really neat physical demonstration is to take two glasses, one of which just fits inside the other with a little bit of a gap. Put the glasses together this way and fill the space between with glycerine. Using a straw or a pipette, place a drop of colored dye partway down. In fact, you can place several dots of different-0colored dye at different levels. Now smoothly rotate the inner glass through a portion of a turn, or even more than a turn. The ink smears out. Now turn the glass back the other way. Instead of creating a new smear, the action reverses the smear, causing the ink dot9s) to “unsmear” and re=assemble into the original dot. They use this demonstration to explain the phenomenon of “Photon Echoes”, but it’s pretty cool in its own right [http://berkeleyphysicsdemos.net/node/307](http://berkeleyphysicsdemos.net/node/307) ---
**Author:** ![What\_Exit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/what_exit/32/10652_2.png) [@What\_Exit](https://boards.straightdope.com/u/What_Exit)\ **Post date:** [September 5, 2017, 1:17pm UTC](https://boards.straightdope.com/t/reversing-the-polarity/795450/40 "2017-09-05T13:17:34Z")
> [@What\_Exit](#): > > Sorry about that, **it did work**. If you like and I remember, I’ll include the model number of the device in question tomorrow in case some other poor soul has to maintain a twinax printer or terminal in this modern age. So the device in Question is a BOS4808R or BOS 4808 and need to go into the e-TwinSt@r HTTP configurator. [Previous page](https://boards.straightdope.com/t/reversing-the-polarity/795450.md?page=1) [Next page](https://boards.straightdope.com/t/reversing-the-polarity/795450.md?page=3)