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Electrical Units

I will give the old-fashioned version of this saga, in which one picks either VOLTS or COULOMBS as the ``fundamental'' unit and derives the rest from that. Today the AMPERE [A] is actually the most basic unit; it is defined to be the current required to flow in both of two ``very long'' parallel wires 1 m apart in order to give a magnetic force per unit length of exactly   $2 \times 10^{-7}$ N/m acting on each wire. No, I'm not kidding. Then the COULOMB [C] is defined as the electric charge that flows past any point in 1 s when a steady current of 1 A is maintained in a wire. I.e. we have 1 C = 1 A-s. Anyway, I will start with COULOMBS because it is more mnemonic.