Direct current (DC) circuit analysis deals with constant currents and voltages, while alternating current (AC) circuit analysis deals with time-varying voltage and current signals whose time average values are zero. Circuits with time-average values of non-zero are also important and will be mentioned briefly in the section on filters. The DC circuit components considered in this course are the constant voltage source, constant current source, and resistor. Electronics also deals with charge Q, electric and magnetic fields, as well as, potential V. We will not be concerned with a detailed description of these quantities but will use approximation methods when dealing with them. Hence electronics can be considered as a more practical approach to these subjects. For the details look at your classical physics and quantum mechanics courses.