Classification of circuit elements

Classification of Network elements 

All the circuit elements in the electrical circuits can be classified into various types based on the following five classifications:

Active and Passive elements

(go to Active and Passive elements for full article)

In electrical networks the elements which deliver power to the circuit

Time variant and Time invariant Elements

Time invariant elements

An element or a system is said to be time invariant if parameters of the element do not vary with time. For example a resistor is a time invariant element whose value of resistance R or any response by it remains same irrespective of the instant of time when the voltage or current is applied to it. Its value may change with change with change in voltage or current like in a non-linear resistor but still it is called as a time invariant element as long as its response won't with respect to time. The given below figures shows

Linear and Non Linear Elements

Linear Element:

An element or a system is said to be linear if it obeys the principles of additive and homogeneity. For a linear element the current passing through it is always proportional to the voltage across it. Practicallyperfect linear elements are seldom found and show some non-linearity, but approximations are made for simplifying the computations.  The V-I characteristics of linear elements pass through the origin.

Homogeneity Property:

When I₁ is the circuit current for applied voltage V₁, then for applied voltage αV₁ the circuit current should be αI₁. Where α is a constant. 

homogeneity

Additive Property:

If I₁ is the current for applied voltage V_1, I₂ is current for Voltage V₂ then for applied voltage V₁+V₂ the current should be I₁+I₂.

Examples: ohmic resistances, conductors etc.

Additivity

Non-linear Elements:

All the elements which are not linear and do not obey the principles of homogeneity and additive properties are called non-linear elements. A nonlinear element doesn't obey ohm’s law.

Examples: diodes and other semiconducting materials, non-linear resistors etc.

Also Read

Classification of circuit elements
Active and passive elements
Unilateral and bilateral elements
lumped and distributed elements

Active Elements and Passive Elements

The elements or components in electrical circuits can be classified in to either active or passive elements or components. Active elements are the energy sources which deliver power to the network whereas passive elements are the elements in the network which consume energy.

Active Elements

Power supply elements such as voltage sources and current sources either independent or dependent which deliver power are called active elements. For an active element the ratio of the voltage across it to the current flowing is negative i.e. \[\frac{V}{I}<0\]. For Non-linear elements \[\frac{dV}{dI}<0\].

The graphical representations of active elements can be as follows.

characteristics of active elements

Passive Elements

The elements which consume energy are called passive elements. These elements either convert energy into another form or store energy in electric or magnetic field. The elements such as a resistor, inductor and capacitor are called passive elements. For linear passive elements the ratio of voltage to current is positive i.e \[\frac{V}{I}>0\] and for Non-Linear elements \[\frac{dV}{dI}>0\]

Characteristics of passive element