Hi, I'm having some difficulties understanding some elementary physics concept. When different emf is supplied to a resistor of the same resistance, the p.d. across changes in different scenarios. By definition, p.d. is the amount of electrical energy converted to other forms of energy per unit charge. Why does the same resistance converts different amounts of energy? Can anyone kindly come up with an analogy? Because I can't find any explanation to this. And why does the charge-carriers want to lose all the energy given to them by the source?