2642: Meta-Alternating Current

2025-07-01T20:57:29Z

2A0B:F4C2:2:0:0:0:0:37: Clarified title text joke

This page is for the [[:Category:Cursed Connectors|Cursed Connectors]] comic with this number. For the 4th of July comic that was replaced by this one, see [[No One Was Hurt]].

{{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==
This is the sixth installment in the series of [[:Category:Cursed Connectors|Cursed Connectors]] and presents Cursed Connectors #120: Meta-alternating current extension cord. It follows [[2589: Outlet Denier]] (#78) after about 4 months and was followed about 1.5 years later by [[2880: Sheet Bend]] (#46).

{{w|Direct current}} is a unidirectional flow of electrons from a power source to something being powered, through one or more conductors, before returning to the power source via one or more other conductors, thus completing the circuit. Batteries produce direct current. It is commonly used in electronics applications, including computers. {{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 typical {{w|power inverter}} efficiency is 90%, and maximum {{w|bridge rectifier}} efficiency is about 99% for 120 V,{{actual citation needed}} so an {{w|extension cord}} made in this manner would lose about 11% power (compounded) per such pair. For the wire shown in the comic, with seven pairs, the efficiency would be 0.89<sup>7</sup>, which is 0.45, that is, 45%.

The title text bemoans that a second inverter doesn't reverse what the first inverter does. The joke here is that in common parlance, to "invert" something is to turn it upside down, obviously doing this twice ends up with the object right side up again as it started. However as used with regard to electricity, an "inverter" changes DC power to AC power. You can't use another inverter to change back to DC. Rather, a separate device, a {{w|rectifier}}, also pictured in the comic, must be used for this second conversion. (However, a similar circuit to an inverter may be used to rectify in a process called {{w|active rectification}}.)

==Transcript==
:[Above the drawing there is a header. Below the header is a chain of rectifiers and inverters. There are seven pairs of rectifiers (the smaller ones) and inverters (the big chunky ones). The first five inverters have arrows pointing to them from a label above the chain, whereas the last five rectifiers are labeled below the chain, but also with arrows pointing to them from that label. The chain starts on the left with a mains plug (type B), followed by the first rectifier. It ends with the last inverter, and a female mains plug (type B socket) to the right. Beneath the chain there is label for the connector and an explanation in brackets below that.]
:Cursed Connectors #120
:Inverters
:Rectifiers
:Meta-alternating current extension cord
:(alternates between AC and DC)

==Trivia==
*This comic replaced [[No One Was Hurt]] as comic 2642 after it was taken down from [[xkcd]]'s website.
**See why on that comic's explanation.
*This comic initially did not have a high-resolution (2x) image for high-DPI displays, making it look more blurry than usual on such devices (such as smartphones). This was probably because it was uploaded hastily to replace No One Was Hurt quickly. It has since been updated to include a high-resolution version.

{{comic discussion}}

[[Category:Cursed Connectors]]

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2642: Meta-Alternating Current