Editing 643: Ohm

{{comic
| number    = 643
| date      = September 30, 2009
| title     = Ohm
| image     = ohm.png
| titletext = More generally, with great power comes great dEnergy/dt
}}

==Explanation==
{{incomplete|This explanation is very messy. Punctuation is all over the place, capitalization is very strange, and much of it is redundant, especially with the two subheadings. I'd fix it, but I don't understand anything about electricity or Ohm's law, so I'm worried I'd screw it up further.}}

This comic deliberately [https://en.wiktionary.org/wiki/conflate conflates] the origin story of the comic-book superhero of {{w|Spider-Man}} with the origin of {{w|Ohm's law}}, as both the origin story of spider-man and Ohm's law deal with power, though the power is of different types.

In Spider-man {{w|Peter Parker}} (who would become Spider-man) is advised by his father figure, his uncle, that "with great power comes great responsibility," where power is defined as the capacity to take action. Not following this advice later leads to his Uncle's death. In contrast, in the xkcd comic Ohm's law is delivered to {{w|Georg Ohm}} in the form of relating current and resistance to power (in the unit of {{w|Watt}}s), where power is defined as energy per unit time. 

The humor lies in the improbability of this scenario, the comparison with Spider-man, as well as the play on the different definitions of power 

The title text defines power in terms of a simple {{w|differential equation}}. Read literally it says that with great power comes a great absorption of energy (dE) per unit time (1/dt), but taken as a definition it says that "power = energy per unit time". In many engineering and physics books the equations are provided in algebraic form as well as differential form as the differential form is more adaptable to special cases, and therefore more general.

===Spiderman===
The uncle's advice references the origin story of the comic-book superhero Spider-Man. In various versions of Spider-Man's origin story, a teenage Peter Parker is brought up by his aunt May and uncle Ben. Uncle Ben cautions Peter that "with great power comes great responsibility," referring to "power" as "capacity to take action". Through an incident involving a spider and some cutting-edge technology, Peter Parker acquires spider-like powers — great strength and the ability to adhere to walls and ceilings. Parker fails to use his new powers to stop a criminal, who then mugs and fatally shoots Uncle Ben. This failure to save his uncle haunts Parker and drives him to use his new powers for heroic purposes. Visually, this comic looks like the dying Uncle Ben counseling his nephew to use his power responsibly.

===Georg Ohm and Ohm's Law===
The unit, Ohm, is named for physicist {{w|Georg Ohm}} who determined experimentally that (within a reasonable range of values) a given resistor would pass double the current when the electrical pressure ({{w|voltage}}) was also doubled. Current flowing through a resistor dissipates power, mostly in the form of heat or light. 

This relationship is summarized by {{w|Ohm's law}}:
:Current = Voltage / Resistance (I=V/R)
:Voltage = Current x Resistance (V=IR)
:Resistance = Voltage / Current (R=V/I)

{{w|Atomic power}} is defined as:
:Power = Current x Voltage (P=IV - {{w|Joule heating|Joule's first law}})
:or by replacing "Voltage" with "(Current x Resistance)" (from Ohm's law):
:Power = Current x (Current x Resistance) = Current² x Resistance

==Transcript==
:[A Cueball-like guy (Ohm) is kneeling behind and holding his Cueball-like uncle by the shoulders as he is lying down.]
:Uncle: Remember: With great power comes great current squared times resistance.

:[Caption below the frame:]
:Ohm never forgot his dying uncle's advice.

{{comic discussion}}
[[Category:Comics featuring Real People]]
[[Category:Comics featuring Cueball]]
[[Category:Multiple Cueballs]]
[[Category:Physics]]
[[Category:Math]]