Monday 22 April 2019

Basic electrical

Basic Elements & Introductory Concepts

Electrical Network:
        A combination of various electric elements (Resistor, Inductor,
Capacitor, Voltage source, Current source) connected in any manner what so ever is
called an electrical network. We may classify circuit elements in two categories, passive
and active elements.

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

Active Element:
               The elements that supply energy to the circuit is called active element.
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.

Bilateral Element:
             Conduction of current in both directions in an element (example:
Resistance; Inductance; Capacitance) with same magnitude is termed as bilateral element.

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

Meaning of Response:
         An application of input signal to the system will produce an
output signal, the behavior of output signal with time is known as the response of the

Linear and Nonlinear Circuits
Linear Circuit: Roughly speaking, a linear circuit is one whose parameters do not
change with voltage or current. More specifically, a linear system is one that satisfies (i)
homogeneity property [response of α u t( ) equals α times the response of u t( ), S ut ( () α )
= α Sut ( ( )) for all α ; and ] (ii) additive property [that is the response of system due
to an input (
u t( )
11 2 2 α ut ut () () +α ) equals the sum of the response of input 1 1 α u t( ) and the
response of input 2 2 α u t( ), 11 2 2 S ut ut ( () ( α +α )) = 11 2 2 α Su t Su t ( ( )) ( ( )) +α .] When an
input is applied to a system “ ”, the corresponding output response of the
system is observed as respectively. Fig. 3.1 explains
the meaning of homogeneity and additive properties of a system.

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