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Difference between active elements and passive elements.

Active Elements

Definition:-

The elements which are in act to increase the power (energy) in the circuit are called as Active Elements.

 Power dissipated by the active element in the circuit = negative(-)
Power(P) = - [Voltage(V) . Current(I)]
Or P = - (I2 . R)
Or P = - (V2 / R)
Or P = V2 / (-R)

 In other words, "The elements having negative resistance are called as Active Elements".

Examples:-

Examples of active elements are energy sources (voltage and current sources), generators and amplifying components such as transistors, triode valves and tunnel diodes etc.

Note:- Keep in mind that amplifiers are active element because they amplify weak signals. In other word they increase the value of current and voltage, hence increase the power (P=V.I). For this reason they are also called as active elements.

 I'm sure now you're thinking about transformers. Perhaps, you have listened or read somewhere before, "The transformers are passive element and not active element". Why? Because they only step up the voltage on the secondary winding but at the same time current decreases on the secondary winding in such a way so that the multiplication of current and voltage on the both primary and secondary windings are always same. It means, there is no power (energy) increament in the circuit due to the transformers.

Now, it is clear that the transformers are not active elements.

Passive Elements

Definition:-

The elements which are not in act to increase the power (energy) in the circuit are called as Passive Elements.

 Power dissipated by the active element in the circuit = positive(+)
Power(P) = + [Voltage(V) . Current(I)]
Or P = + (I2 . R)
Or P = + (V2 / R)

Or P = V2 / (+R)

 In other words, " The elements having positive or zero resistance are called as Passive Elements".

 Remember that there is not any element having zero resistance exists in the world.

Examples:-

Examples of passive elements are resistors, inductors capacitors and diodes (except tunnel diode).

Note:- Don't be confused with the definition of passive elements. In the definition it is clearly said that the elements should not increase the power (energy) in the circuit. It means, the elements may decrease the power of the circuit or may not play with the power of the circuit, i.e. power decreases or remains constant.

Now, a question should not arise in your mind, how inductors, capacitors and transformers are passive elements. The question might be arisen because they don't consume power in the circuit.
active elements, passive elements, active, passive, elements, circuit

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