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 direction of electron flow, and is commonly used for longer-distance transmission (such as from the power plant to an outlet).

This comic proposes a humorous ''Meta-Alternating Current'', which uses a series of adapters to "alternate" between DC and AC current along the length of a connector. This is absurd in part 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 some aspect of the input. In mathematical contexts the inverse of an inverse is the original object. For a DC power supply we might have supposed that what is inverted is polarity between the input and output, something that would be easily done at high efficiency by just 'crossing' (without connecting between) the wires coupling the inputs and outputs. Applied to AC, it would shift the phase by 180°. 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 and the final AC phase will have no bearing with the original, should that have any practical significance, though the frequency and magnitude ought to be sufficiently on-target.

==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]]