Introduction

Unit-I

Introduction

CLASSIFICATION OF CIRCUIT ELEMENTS

In electrical circuits, we can classify the circuit elements mainly as

(a) active elements (energy sources)

They are voltage and current sources.

Example: Generators, Vacuum tubes, transistors etc.

(b) passive elements :

These elements either dissipate energy in the form of heat or store energy.

Example: R, L and C. R dissipates energy in the form of heat. L stores energy in its magnetic field. C stores energy in its electrostatic field.

ELECTRICAL NETWORK

The connection of passive and active elements by means of conductors is called an active network. If the active sources are absent, it is called passive network.

LUMPED AND DISTRIBUTED ELEMENTS

Physically separate elements such as resistors, capacitors and inductors are called lumped elements.

A distributed element is one which is not separable for electrical purposes. A transmission line has distributed resistance, capacitance and inductance along its length.

BILATERAL AND UNILATERAL ELEMENTS

In a bilateral element, the voltage current relation is the same for current flowing in either direction. A unilateral element has different relations between voltage and current for the two possible directions of current.

Example for bilateral elements: resistor, inductor and capacitor.

Example for unilateral elements: vacuum tubes, silicon diodes, metal rectifiers etc.

LINEAR AND NON-LINEAR ELEMENTS

An element is said to be linear, if it satisfies the linear voltage-current relationship. It means that for linear elements, the relation between V and I is linear. For example the current passing through a resistor is proportional to the voltage applied. All elements which do not satisfy the linear voltage - current relationship are called non-linear.