They actually both come from Latin: i. stands for id est and means roughly "that is"; stands for exempli gratia, which means “for example”. But this graphic's explanation is a bit easier to remember than the Latin definitions.
Infographic: ElectricityA visual cheat sheet about electrical physics, containing the most important formulas of current and Ohm’s law expressed through an impossible water circuit analogy.(by Pierluigi Scotolati)
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