Basic Elements & Introductory Concepts
 
Electrical Network: A combination of different electric elements (like Inductor, Resistor, Capacitor, Voltage source, Current source) associated in any manner what so ever is termed as an electrical network. We might categorize circuit elements in two groups, passive and active elements.

Passive Element: The element that receives energy (or absorbs energy) and then either transforms it into heat (R) or stored it in an electric (C) or magnetic (L) field is termed as passive element.

Active Element: The elements which supply energy to the circuit are termed as active element. Illustrations of active elements involve voltage and current sources, generators, and electronic devices which need power supplies. The transistor is an active circuit element, meaning which it can amplify power of a signal. On other hand, transformer is not an active element since it does not amplify the power level and power stays same both in primary and secondary sides. Transformer is an illustration of passive element.   

Bilateral Element: The conduction of current in both directions in an element (illustration: Inductance; Resistance; Capacitance) with similar magnitude is known as bilateral element.

Unilateral Element: Conduction of current in one direction is known as unilateral element. (Illustration:Transistor,Diode)element.

Meaning of Response: The application of input signal to the system will generate an output signal; the behavior of output signal with time is termed as the response of the system.