Q. Briefly Explain Energy and Power?

If a charge dq gives up energy dw when going from point a to point b, then the voltage across those points is defined as

v = dw/dq

If dw/dq is positive, point a is at the higher potential. The voltage between two points is the work per unit positive charge required to move that charge between the two points. If dw and dq have the same sign, then energy is delivered by a positive charge going from a to b (or a negative charge going the other way). Conversely, charged particles gain energy inside a source where dw and dq have opposite polarities.

The load and source conventions are shown in Figure, in which point a is at a higher potential than point b. The load receives or absorbs energy because a positive charge goes in the direction of the current arrow from higher to lower potential. The source has a capacity to supply energy. The voltage source is sometimes known as an electromotive force,or emf, to convey the notation that it is a force that drives the current through the circuit.