On all about circuits I keep seeing E in tables like this:

Table of values with E

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..

  • \$\begingroup\$ Struggled to think of a tag - so feel free to retag. \$\endgroup\$ – Dean Jan 5 '12 at 20:22
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    \$\begingroup\$ Voltage is technically electomotive force in the particular units of Volts. Since Volts is so overwhelmingly used, we usually get lazy and say "Voltage" even when we don't really care about the units and should say "electromotive force", sometimes abbreviated EMF. EMF is like "distance", wheras voltage is like "inch measurement". \$\endgroup\$ – Olin Lathrop Jan 5 '12 at 20:42
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    \$\begingroup\$ @OlinLathrop I think your comment is a better answer then both mine and Chris's! \$\endgroup\$ – Kellenjb Jan 5 '12 at 20:46

"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.

  • \$\begingroup\$ I don't know how to make this answer in more detailed, but hopefully this answers it for you. \$\endgroup\$ – Kellenjb Jan 5 '12 at 20:31
  • \$\begingroup\$ We were taught "CIVIL" not "Eli the Ice Man", I think I prefer "Eli the Ice Man". \$\endgroup\$ – Dean Jan 6 '12 at 17:34
  • \$\begingroup\$ I (for current) stands for INTENSITY, and Q (for charge) stands for QUANTITY. \$\endgroup\$ – jp314 Feb 13 '16 at 17:19

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.


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