We know that if a current is entered through the positive polarity of an element and exit through the negative polarity, then the power is positive which means that the power is consumed through the element. On the other hand, if the current is entered through the negative terminal then the power is negative which means that the element has generated power to any external element connected to it. My question is that I need to understand the physics behind this "rule" in an easy way. Thanks in advance.
Edit: I need to understand the physical reason behind this convention. For example, why specifically if the current enters the + terminal then the power is dissipating in the element why this is not the case if the current enters from the -ve terminal?
Edit 2: Ok Guys I think I have an explanation but I am not sure of it. When the current enters from a positive terminal and exits from the negative terminal, this means that the charges did enter from a point of high energy (high volt) and exit from a point of low energy (low volt) this means that the charges while they have passed through the element they have lost some energy and therefore this lost energy is absorbed by the element according to the law of conservation of energy. The opposite can be said if the element where generating energy. So is this explanation is right?