Firstly what is a circuit?
In simple words, a circuit is a closed path in which the electrons flow in it.
Here we learn about the classification of the elements.
We all know about the basic concepts of Resistance ,Inductance ,Capacitance and about the ohm's law.
Linear and non-linear element
When we think about the word linear the first thing that comes to our mind is what we studied in high school mathematics as linear is a straight line with an equation y = mx + c.
A system is said to be linear when system output is related to the input.
The same concept is applied here as an element is said to be linear when it's VI characteristics as follows.
- Only one equation of straight line passing through the origin for all values of I.
For example take this graph here it is linear.
All these graphs are non-linear examples.
The first graph clearly shows that it is a non-linear graph.
The second graph passes through the origin but not for all positives values. So it doesn't satisfy the condition for linearity.
Therefore it is also a non-linear graph for which it resembles the non-linear element.
The third graph by the way it passes through the origin but after certain point it is saturated. Overall it doesn't satisfy the linearity condition so this is also non-linear.
Active and passive element:
Active element or active sources are something which supplies power to the circuit.
Some of the examples of active sources are the voltage source and the current source and also the transistor.
Passive elements are something which consumes power from the sources.
Some common examples of passive elements are resistors, inductors and capacitors. Where they all are considered as passive only if R>=0 , L>=0 and C>=0.
When we take the VI characteristics to find out the active and the passive elements then it totally depends on the quadrant where we find the slope.
In order to have a clear understanding kindly look at the below graphs.
We all know All Silver Tea Cups where we use this in a trigonometry to find an angle specifying each of the quadrant.
Likewise take a note that we need to find the slope tan θ.
Where we know that in the first and the third quadrant the tan θ will be positive in that case it is a passive element.
In simple words, when the slope is positive then it is a passive element and if the slope is negative then it is an active element.
Therefore the slope will be positive and hence it is a passive element which is determined by the VI characteristics.
Now here we have only third quadrant so it is the passive element.
So this is an active element which can be easily predicted from the VI characteristics.
