Current and Ohm's Law

The term electromotive force is an antique expression for the modern term voltage.
Current is the bulk motion of electric charges. The units of current are amperes = Coulombs per second.
Current is always defined to flow from high (positive) to low (negative) voltage. When a current is carried by electrons, the electrons move opposite to the direction of the current.
Continuing the analogy between the electric potential and the gravitational potential: just as water flows from high elevations to low elevations, so current flows from high voltages to low voltages.
In some materials, the amount of current depends linearly on the voltage across a material; such materials obey Ohm's Law:
```
             I 
           -----  = const     or      V = IR
             V
```
where R is the resistance of the material.
However, many materials do NOT obey Ohm's Law -- it is not universal.

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