Reverse the polarity!

Post your reality fanfiction here.

Moderators: gmalivuk, Moderators General, Prelates

User avatar
Heimhenge
Posts: 372
Joined: Thu May 01, 2014 11:35 pm UTC
Location: Arizona desert

Reverse the polarity!

Postby Heimhenge » Sat Jul 06, 2019 11:05 pm UTC

I did a forum search for "reverse polarity" and didn't find much on my topic, so here goes ...

We've all gotten used to some engineer (pick your story) suggesting that "reversing the polarity" might solve the problem. Sometimes its a deflector shield, sometimes a particle beam or other weapon, and sometimes just something that's "broke" and needs to work again, or not broke but needs to perform differently.

I've tried to imagine real-world scenarios where reversing the polarity actually accomplishes something useful but it's tough to come up with a believable example. I'm not talking about something that just works with either polarity, like a DC incandescent light bulb. I'm talking about doing something useful when the original polarity doesn't do it. I've been unable to come up with a solely electric/magnetic example.

Closest I can get is when my plastic-bladed weed wacker was just too worn and dull to cut much. It ran off a rechargeable battery. The backs of the blades weren't "sharpened" like the fronts ... they were like 1/4" thick with sharp square edges. So just for the helluvit I reversed the polarity to make the blades spin backwards and sure enough, it started cutting pretty good again. I think it was those 90° edges. Worked for another season until those edges got rounded off.

But that example kinda stretches the science fiction trope.

Can anyone suggest a real-world example of where "reversing the polarity" actually accomplishes something? Not like I'm writing a story about this, but that trope comes up so often I gotta wonder how it got started.

ijuin
Posts: 1110
Joined: Fri Jan 09, 2009 6:02 pm UTC

Re: Reverse the polarity!

Postby ijuin » Sun Jul 07, 2019 3:43 am UTC

Pretty much anything that uses a magnetic/electromagnetic field to move something or exert a mechanical force is going to pull/move in the opposite direction with reversed polarity. On the other hand, anything using electronic logic circuits is going to fail outright because most such circuits use diodes (one-way gates) in them, which prevents current from going backwards.

User avatar
Heimhenge
Posts: 372
Joined: Thu May 01, 2014 11:35 pm UTC
Location: Arizona desert

Re: Reverse the polarity!

Postby Heimhenge » Sun Jul 07, 2019 7:39 am UTC

ijuin wrote:Pretty much anything that uses a magnetic/electromagnetic field to move something or exert a mechanical force is going to pull/move in the opposite direction with reversed polarity. On the other hand, anything using electronic logic circuits is going to fail outright because most such circuits use diodes (one-way gates) in them, which prevents current from going backwards.


Yeah, I learned that the hard way when rewiring a PC speaker and confusing logical ground with system ground.

User avatar
Eebster the Great
Posts: 3463
Joined: Mon Nov 10, 2008 12:58 am UTC
Location: Cleveland, Ohio

Re: Reverse the polarity!

Postby Eebster the Great » Sun Jul 07, 2019 8:42 am UTC

Repeatedly reversing the polarity of a magnet is a good way to generate an alternating current.

User avatar
gmalivuk
GNU Terry Pratchett
Posts: 26767
Joined: Wed Feb 28, 2007 6:02 pm UTC
Location: Here and There
Contact:

Re: Reverse the polarity!

Postby gmalivuk » Sun Jul 07, 2019 12:59 pm UTC

Reverse the polarity! Now reverse it again! And again! And again! And again! And again! And again! And again! And again! And again! Okay you're doing great, but could you try to speed that up to about 60 times per second?
Unless stated otherwise, I do not care whether a statement, by itself, constitutes a persuasive political argument. I care whether it's true.
---
If this post has math that doesn't work for you, use TeX the World for Firefox or Chrome

(he/him/his)

User avatar
Eebster the Great
Posts: 3463
Joined: Mon Nov 10, 2008 12:58 am UTC
Location: Cleveland, Ohio

Re: Reverse the polarity!

Postby Eebster the Great » Sun Jul 07, 2019 1:25 pm UTC

gmalivuk wrote:Reverse the polarity! Now reverse it again! And again! And again! And again! And again! And again! And again! And again! And again! Okay you're doing great, but could you try to speed that up to about 60 times per second?

Spoiler:
Image

User avatar
ucim
Posts: 6860
Joined: Fri Sep 28, 2012 3:23 pm UTC
Location: The One True Thread

Re: Reverse the polarity!

Postby ucim » Sun Jul 07, 2019 2:46 pm UTC

When setting up a stereo, if the bass sounds weak, reverse the polarity of one of the speakers. (Speakers out of phase tend to cancel each other out; the effect is most noticeable at long wavelengths.)

Jose
Order of the Sillies, Honoris Causam - bestowed by charlie_grumbles on NP 859 * OTTscar winner: Wordsmith - bestowed by yappobiscuts and the OTT on NP 1832 * Ecclesiastical Calendar of the Order of the Holy Contradiction * Heartfelt thanks from addams and from me - you really made a difference.

ijuin
Posts: 1110
Joined: Fri Jan 09, 2009 6:02 pm UTC

Re: Reverse the polarity!

Postby ijuin » Sun Jul 07, 2019 5:04 pm UTC

And then you can reverse the other speaker for twice the improvement!

User avatar
Heimhenge
Posts: 372
Joined: Thu May 01, 2014 11:35 pm UTC
Location: Arizona desert

Re: Reverse the polarity!

Postby Heimhenge » Sun Jul 07, 2019 6:02 pm UTC

ucim wrote:When setting up a stereo, if the bass sounds weak, reverse the polarity of one of the speakers. (Speakers out of phase tend to cancel each other out; the effect is most noticeable at long wavelengths.)

Jose


Thanks! Now that's the first example that comes close to fitting the trope. I actually did that once and forgotten about it. BTW, all this discussion about alternating current doesn't really apply.

Nicias
Posts: 168
Joined: Tue Aug 13, 2013 4:22 pm UTC

Re: Reverse the polarity!

Postby Nicias » Mon Jul 08, 2019 6:30 pm UTC

What about plugging in a USB Type A connector?

ijuin
Posts: 1110
Joined: Fri Jan 09, 2009 6:02 pm UTC

Re: Reverse the polarity!

Postby ijuin » Mon Jul 08, 2019 7:13 pm UTC

USB connectors other than type C are deliberately made asymmetrical in order to prevent this. Even if you could get the plug into the socket, the wires would be on the wrong face to connect.

If you could connect a USB cable with the wires in reverse order, then the power leads would be where the data leads should be, and would probably burn out some circuits.

User avatar
Eebster the Great
Posts: 3463
Joined: Mon Nov 10, 2008 12:58 am UTC
Location: Cleveland, Ohio

Re: Reverse the polarity!

Postby Eebster the Great » Mon Jul 08, 2019 8:11 pm UTC

Reversing the polarity of a speaker is a good way to make a microphone in a pinch.

User avatar
Zamfir
I built a novelty castle, the irony was lost on some.
Posts: 7594
Joined: Wed Aug 27, 2008 2:43 pm UTC
Location: Nederland

Re: Reverse the polarity!

Postby Zamfir » Tue Jul 09, 2019 8:50 am UTC

Thanks to Cracked and TVTropes (intellectual touchstones of the 21st century), here's apparently the source of the phrase:
https://www.cracked.com/article_19949_the-6-most-important-sci-fi-ideas-were-invented-by-hack.html

Spoiler:
"Reverse the polarity" is what science fiction characters tend to say or shout when they need a science-fictiony-sounding solution to a difficult problem -- it's most often heard in old B-movies like Forbidden Planet (Leslie Nielsen says it there) and classic sci-fi shows like Doctor Who, where "Reverse the polarity of the neutron flow" even became a catchphrase for the Third Doctor.

Of course, in all those situations, "reversing the polarity" shouldn't really do s**t: Neutrons don't even have an electric polarity, which is why they're called neutrons. It's just meaningless technobabble that hack writers like to use as shorthand for "I can't be arsed to look up some actual science, and I'm hoping you won't notice." Being the hackest of all writers, Serviss didn't just use the exact same term in Edison's Conquest, several decades ahead of everyone else; he also somehow managed to do it multiple times within the same book.

Chapter II: "... by varying the potential or changing the polarity ..."
Chapter V: "... this charge, it was evident, was opposite in polarity ..."
Chapter VI: "... and reversing their polarities the members of the squadron ..."
Chapter VIII: "... after they had reversed their polarity, and applied their intensifier ..."
Chapter IX: "... instantly reverse polarities ..."

Counting paraphrasing and the like, we found nine instances of "reversing the polarity" in Edison's Conquest, which, according to TV Tropes, is seven more times than it's used in all of the original series of Star Trek. The most shocking part, however, is that the phrase is actually used pretty consistently: According to the book, Edison's ships have the power to change (reverse) their own magnetic charges (polarity), which causes them to be repelled from celestial bodies and thus travel near the speed of light ... which still makes zero f*****g sense, but at least he made an effort. The War of the Worlds may be the respected literary classic, but how many meaningless catchphrases did it spawn?


It does leave a gap between Serviss's book in 1898, and Forbidden Planet in 1956. Perhaps the writers of Forbidden Planet had read the book, or there are lost steps in between, or they reinvented the phrase. The meaning in Forbidden Planet is the same. They reverse polarity during landing, to switch the spaceship from attracting mode to repelling the planet. Anti-gravity that works similar to electromagnetism.

Forbidden Planet was a fairly major movie, so we can assume that later use of the phrase were directly or indirectly derived from there. In particular, through 1960s Doctor Who and Star Trek.

User avatar
Heimhenge
Posts: 372
Joined: Thu May 01, 2014 11:35 pm UTC
Location: Arizona desert

Re: Reverse the polarity!

Postby Heimhenge » Fri Jul 12, 2019 12:13 am UTC

Interesting you should bring up Forbidden Planet. That brain enhancement thingy was able to materialize a creature capable of killing the person who brought it into being. That would seem to be the brain, or the materialized creature, violating the First Law by killing itself. Or maybe the Third Law?

Been active in another thread that makes me wonder: viewtopic.php?f=59&t=125362

Still curious about that creature ... like was it literally an alter-ego of Morbius? Or did it have any real autonomy?


Return to “Fictional Science”

Who is online

Users browsing this forum: No registered users and 5 guests