- Power $p(t)=\frac{dE}{dt}$ - When circuit is completed within conductor, electrons not longer flow freely as positive/negative terminals are created, moving towards the positive terminal. Rate of change of charge is called current $i(t)=\frac{dq}{dt},q=\int i(t)dt+q(0)$ - Current is directional. If we define $i$ to be positive from $a$ to $b,$ we can define $-i$ as going in the opposite direction with the same magnitude - Current flows from positive to negative in conventional flow - Voltage $v=\frac{dE}{dq}$, change in energy per charge- difference in potential between point 1 and point 2. Positive minus negative side - Elemental voltage is potential difference between two points its connected to