Everybody knows that devices stop working when you let the magic smoke out.Typically a Cartesian graph uses the X axis for the independent variable (the one you can change at will) and the Y axis for the dependent variable (the one that is a function of the other). That is the convention.
It is oft the case that following that convention will result in a graph that displays some information in a useful fashion.
That is all it is.
The same convention is followed when either variable may be the driving force. For example, you may control the voltage across a diode to read the current, or drive the current and read the voltage. Either way works, but by convention voltage is shown on X, current on Y.
Also, Ohm’s Law is an empirical approximation over a limited span. For example, if I put 100 volts across a 1 ohm ½ watt resistor Ohm’s law predicts I get a constant 100 amps of current.
In reality I get a brief current followed by a bang and some smoke. Don’t try this at home!
by Jake Hertz
by Aaron Carman