Its change law obeys ohm's law of active circuit, and its mathematical expression is: u = e-IR.
Where U is the terminal voltage and Ir is the internal voltage of the power supply, also called internal voltage drop. For a given power supply, both electromotive force e and internal resistance r are certain. As can be seen from the above formula, the terminal voltage u of the circuit is related to the current in the circuit. When the current I increases, the internal pressure drop Ir increases and the terminal voltage U decreases. On the contrary, when the current I decreases, the terminal voltage u increases.
The application scope of ohm's law of the whole circuit: pure resistance circuit, energy conversion in closed circuit;
E=U+Ir,ei =UI+I 2r,pRelease = EI,pOutput = ui。
In a pure resistance circuit
P output = I 2r = e 2r/(r+r) 2 = e 2/(r 2+2r+r 2/r), when r=R, p output is the largest, and p output = e 2/4r (mean inequality).