History Main / ReversePolarity

--->It doesn't.
** Episode "[[Recap/StarTrekTheNextGenerationS1E2TheNakedNow The Naked Now]]". Near the end of the episode the Enterprise crew needs an extra minute so they can repair their engines in order to escape an incoming object. [[CreatorsPet Wesley Crusher]] reverses the power leads on the ship's TractorBeam to turn it into a repulsor beam to push off another ship and give them the time they need.

* ''ComicBook/DisneyDucksComicUniverse'': A Creator/CarlBarks comic is the earliest recorded use of ReversePolarity as technobabble, dating all the way back to March 1961 ([[http://coa.inducks.org/issue.php?c=us/US+++33#02 US #33]]) in "Billions in the Hole".

* Creator/RobertAHeinlein's YellowPeril novel ''Literature/SixthColumn'' features two kinds of ReversePolarity used with the book's race-specific-DeathRay. The first way turns it in to a [[LiquidAssets health-ray]] ([[MST3KMantra don't think too hard about that]]), and the second way lets you use it on non-Asians.

* {{Antimatter}} is normal matter with ReversePolarity. The charges of protons and electrons are switched.

* Live sound reinforcement mixing consoles have a "phase" switch on every input which is really just a ReversePolarity switch. This is often used when placing two microphones on the same sound source directly facing each other. If there are 2 microphones on a snare drum, one above facing down and a second below facing up, the engineer will usually ReversePolarity on the bottom mic.

* An episode of the ''WesternAnimation/MenInBlack'' Cartoon had a super-power giving device. How do you undo its effects? To paraphrase:

* ''TabletopGame/MagicTheGathering'' made a card for "Reverse Polarity"--any damage taken so far that turn from artifacts is retroactively added to your health total. Lampshaded, but [[BetterThanABareBulb most certainly not explained]], in that the picture shows a mace acting as a HealingShiv.

* ''WesternAnimation/JusticeLeague'' episode "Secret Origins": Batman saves the day by "reversing the ion charge" on an alien ship (this also appeared on the first episode of ''Challenge of the {{WesternAnimation/Superfriends}}'', and very similarly).

* In ''VideoGame/OutOfOrder'', you need to reverse the polarity of your music player by swapping two wires around. This makes the device play music backwards, uncovering some backmasked messages.
* In ''VideoGame/{{Turok}} 2: Seeds of Evil'', one of the missions for the last level is to reverse the polarity of some power cells that generate toxins, causing them to purify the water instead.

When a major obstacle in a ScienceFiction show is resolved purely through the judicious application of TechnoBabble, the characters have successfully Reversed the Polarity. It seems that every futuristic gadget or space ship subsystem performs some miraculous function if only you route the power through it ''backwards''. [[BeamMeUpScotty Urban legend has it]] the expression originated on ''Series/DoctorWho''. In reality, the phrase "Reverse the Polarity" [[OlderThanTheyThink can be traced back at least as far back as]] the 1898 ''Literature/TheWarOfTheWorlds'' sequel ''Edison's Conquest of Mars'' by Garrett P. Serviss. However, it was popularized by ''Series/DoctorWho,'' as Creator/JonPertwee asked the writers for a simple piece of {{Technobabble}} he could reliably deliver. The version most associated with the Third Doctor is "reverse the polarity of the neutron flow", although he [[MemeticMutation only said it once]] during his time as the Doctor and once in a multi-Doctor special.

* In ''Creator/MichaelMoorcock's Multiverse'' the Chaos Engineers manage to reverse the polarity of ''the multiverse itself'', effectively reversing everybody's destiny.

[[folder:Film — Animated]]

* In ''WesternAnimation/TheTransformersTheMovie'', the heroes' ship is targeted by Decepticon missiles. Kup's solution is to reverse the polarity, like he did against the Shrikebats of Dromedan. Hot Rod is afraid it will tear the ship apart; instead it repels the missiles.

[[folder:Film — Live-Action]]
* Used to defeat energy-eating giant square stompy robot in Kurt Neumann's 1957 SciFi film ''Film/KronosDestroyerOfTheUniverse''.
* In ''Film/AustinPowersInGoldmember'', the tractor beam used by Goldmember and Dr. Evil to pull an asteroid to Earth has "Do not reverse polarity" written on a low-tech-looking panel. When Dr. Evil, [[spoiler:having turned good]], does reverse the polarity, the beam destroys the asteroid instead of sending it to Earth.
* The 2007 ''Film/OceansThirteen'' had Creator/BradPitt dismissing Don Cheadle's technobabble by saying, "Becomes magnetized, reverse polarization, I know."
* ''Film/BatmanTheMovie'' (1966): "If I could just... reverse the polarity... send out waves... of super-energy!" Highly effective on torpedoes until... "Confound it! The battery is dead!"
* In the 1952 British film ''Film/TheSoundBarrier''. the hero solved the problem of controlling a supersonic airplane by reversing the flight controls. To increase lift, for example, he pushed the stick forward instead of back as would be expected. This is based on the real-life phenomenon of "control reversal", which is detailed in the RealLife section below.
* In ''Film/TheAvengers2012'', the phrase "reverse the polarity" is used by Tony Stark in a less unacceptable context--Stark is giving Captain America instructions to slow down a turbine engine/motor. As discussed above, reversing the polarity on a basic DC motor will reverse the direction of its rotation, which has the immediate effect of slowing its motion.
* Film/SpyKids

* In ''Film/FrankensteinMeetsTheWolfMan'' (1943), Dr. Frankenstein's journal explains that the practically immortal monster can be killed by attaching him to the machine that gave him life and "changing the poles".
* The 1963 movie ''[[Film/TheAbsentMindedProfessor Son of Flubber]]'' features a rain machine that does not work until they reverse the polarity.
* In the 1996 TV movie ''Gulliver's Travels'' Gulliver reversed the big magnet in the flying island to counter the plot of the people on the ground to crash the island by using another big magnet that attracts the island.

* ''Film/StarTrekGenerations''. Data literally uses the phrase "reverse the polarity" when he opens a magnetic door by attenuating his axial servo. Course, reversing the polarity on a magnetically-controlled door ''would'' open it. Go figure.
* In ''Film/{{Ghostbusters 1984}}'', the Ghostbusters defeat Gozer by crossing the energy streams from their proton packs. This, we are informed, will "reverse the particle flow through the gate." Naturally it works.
** This is an echo of Egon's earlier warning that crossing the streams would cause "total protonic reversal", which presumably means protons flipping to a negative charge (perhaps indicating that they're creating antimatter).
** [[Film/{{Ghostbusters 2016}} The 2016 reimagining]] has a similar case that is better explained - there is a portal releasing paranormal energy. So the Ghosbusters decide to do a "total protonic reversal" on that to make the breach work the opposite way, sucking the ghosts in like one of their traps.
* ''Film/ForbiddenPlanet''. Commander Adams orders a subordinate to "Stand by to reverse polarity" during the initial landing on Altair 4, apparently referring to flipping the engines from "push forward through space" to "push back against gravity". Until an earlier example is found, this 1956 film may be the first time the trope was used.
* One of the many reasons ''Film/FantasticFour2005'' was criticized was its wham-tastic use of this trope. Reed is constantly spouting technobabble, and quite literally, his plan to return the Four to normal is to reverse the polarity of the cosmic rays that gave them their powers.

* In ''Film/TimeChasers'' (best known for its ''Series/MysteryScienceTheater3000'' treatment), the time machine normally goes forward in time; reversing the polarity causes it to go backward in time.
* In ''Film/Apollo13'', the crew reversed the polarity of the power link between the Command Module and the Lunar Module in order to get enough power to restart the Command Module systems for reentry. Unlike most examples, this was a real-life necessity as the LM's power link was intended to power the LM from the Service Module until separation, and reversing the polarity allowed the command module to draw power from the LM.

* ''Film/ResidentEvilTheFinalChapter''. The group enter [[ElaborateUndergroundBase Hive]] via an [[AirVentPassageway air intake]], which requires easing themselves between the blades of a giant turbine. Wesker sees what they are doing and orders "reverse polarity" on the turbine so they will be [[TurbineBlender sucked back into it]]. Saying "reverse the airflow" or "reverse the turbine" would have made more sense, so it's likely just a nod to this trope in sci-fi.