On all about circuits I keep seeing E in tables like this:
In the table I and R make sense with the units. But the E doesn't. So where does it come from?
I was looking at this article on superposition theorem..
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"E" stands for "Electromotive force", which is essentially just voltage. We just have come used to using "V" instead of "E"
It would be the same as asking why Current is "I" even though it is measured as Amps.
Likewise it would also be the same as asking why Resistance is "R" even though it is measured in ohms.
This might also help you understand the saying "Eli the Ice Man" where the E stands for voltage.
The E is just a variable chosen by the author's preference of conventions, but it most likely derives from "Electro Motive Force" which is essentially synonymous with voltage.
I like to think of the E of voltage as energy even though I know the E stands for 'electromotive force'. 1 volt = 1 joule of energy per coulomb of electrons (coulomb = aprox. 6.25 billion x billion electrons) ie. 110v is equivalent to each coulomb being given 110 joules of energy to go out and spend. Similarly 1 amp = a current of 1 coulomb moving through a circuit every second, ie. 10amps = 10 coulombs per second.