Electric Circuit:- An Electric Circuit is a closed path composed of active (Battery, Current Source) and passive elements (Resistor, Inductor, Capacitor) to which current is confined. The example of electric circuit is shown in figure below
Active Elements:- An Active element is one which supplies energy to the circuit. Examples of active elements include voltage and current sources, generators, and electronic devices that require power supplies. A transistor is an active circuit element, meaning that it can amplify power of a signal. On the other hand, transformer is not an active element because it does not amplify the power level and power remains same both in primary and secondary sides. Transformer is an example of passive element. In the circuit shown in fig 1 the battery with voltage “v” is a active Source.
Passive Elements:- Passive element is one which receives energy and converts it into heat or stores energy in the form of electric field or magnetic field. e.g. Resistors, Capacitors and inductors.
Node:- A point at which two or more circuit elements are joined together. in fig 1 the Points “a”, “b”, “c”, “d”, “e”, and “f” are node because at each point two or more circuit elements are joined together. For example at point “a” two circuit elements R1 andR2 are joined together.
Junction:- A point at which three or more branches are joined together. in the fig 1 the points “c” and “d” in are junction points. At point “c” three circuit elements R1, R4 and battery are joined together.
Branch:- A part of network which lies between two junction points is called branch. in the fig 1 the parts “cabd”, “cfed” and “cd” are branches of the circuit.
Linear Circuit:- A circuit whose parameters do not change their values with current or voltage. It is known as linear circuit. ohm’s law can be applied to such circuits. The fig 1 is the example of linear circuit. In fact, a circuit is linear if and only if its input and output can be related by a straight line passing through the origin as shown in figure.
Non-Linear Circuit:- A circuit whose parameters change their values with current or voltage. It is known as Non-linear circuit. ohm’s law cannot be applied to such circuits. The best example of Non-linear circuit is circuit containing diode. Non-linear circuit does not obey the homogeneity and additive properties. Volt-ampere characteristics of non-linear elements are shown in figure below.
Bilateral Circuit:- A circuit whose properties or characteristics are same in either direction is called bilateral circuit. e.g. distribution lines, transmission lines etc.
Unilateral Circuit:- A circuit whose properties or characteristics are not same in either directions is called unilateral circuits. e.g. a circuit containing diode.