Editing 2642: Meta-Alternating Current

{{comic
| number    = 2642
| date      = July 6, 2022
| title     = Meta-Alternating Current
| image     = meta_alternating_current.png
| titletext = It's always bothered me that you can't cancel out an inverter by putting a second inverter after it.
}}

==Explanation==
{{incomplete|Created by a CHAIN OF INVERTERS - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
This comic replaced [[No One Was Hurt]] as comic 2642 after the former was taken down from [[xkcd]]'s website.

In electronics, {{w|direct current}} is a unidirectional flow of electrons from a power source to something being powered, through one or more conductors, before returning via one or more other conductors, thus completing the circuit. It is commonly used for battery-powered appliances. {{w|Alternating current}}, on the other hand, frequently reverses the flow of electrons, and is commonly used for longer-distance use (such as from the power plant to an outlet).

This comic proposes a humorous interspersion, ''Meta-Alternating Current'', which uses a series of adapters to "alternate" between DC and AC current. This is funny because since typical {{w|power inverter}} efficiency is 90%, and maximum {{w|bridge rectifier}} efficiency is 81.2%, an {{w|extension cord}} made of them would lose about 27% power per such pair. The "extension cord" shown would yield about 11% of its input power.

The title text bemoans that an inverter, which converts direct current to alternating current, does not work in the other direction, as a layman's interpretation of the word "inverter" might appear. Rather, a separate device, a {{w|rectifier}}, also pictured in the comic, must be used for this second conversion.

Common understanding of "inverting" would be to turn upside-down, or reverse the input polarity in the output, something that would be easily done at near-zero inefficiency by just 'crossing' (without connecting between) the wires coupling the inputs and outputs. Two such cross-overs would indeed restore the original electrical supply. In the conversion from DC to AC it is instead an active circuit that ''periodically'' inverts, and then uninverts, the effective polarity – with a specific frequency, and usually a voltage conversion, to conform to some AC need such as using a car battery to power a standard household device designed and built for use on a mains supply. A rectifier is a nominally passive circuit that accepts either polarity (e.g. at any given moment of an AC phase) and produces a single definite polarity as output, possibly smoothed out by a buffering capacitance or with additional components to attain a given voltage and amperage.

It may in fact be the case that a campsite use of a rectifying device intended for home use (e.g. a standard phone charger that down-converts household AC to a given DC) requires it to be plugged into an inverter itself powered from a battery system (DC to AC), more inefficiently than a single converter (with the correct voltage/amperage re-regulation) might accomplish the task. Further chaining this into more inverters/rectifiers would normally not be considered.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

Cursed connectors #120

Drawing of a chain of rectifiers and inverters.
There are seven pairs of rectifier/inverter.
The chain starts on the left by a mains plug (type B), followed by the first rectifier. It ends with the last inverter, and a female mains plug (type B socket).

Meta-alternating current extension cord
(alternates between AC and DC)

{{comic discussion}}
[[Category:Cursed Connectors]]