Here is a portion of the explanation my book gives "Kirchoff's second rule follows the law of conservation of energy. Let's imagine moving a charge around a closed loop of a circuit. When the charge returns to the starting point, the charge-circuit system must have the same total energy as it had before the charge was moved. The sum of the increases in energy as the charge passes through some circuit elements must equal the sum of the decreases in energy as it passes through other elements." Why is the sum always zero in his second rule (∑ΔV=0)? Why can't the battery supply a potential difference greater than elements that cause a decrease (∑ΔV>0) ? Or why can't the elements cause a decrease in the potential difference that stops current pass a certain point (∑ΔV<0)?