BASIC CIRCUIT COMPONENTS

Electric Circuit:

               The interconnection of various active and passive components in a prescribed manner to form a closed path is called an electric circuit.

Active Components:

             An active component is a component which supplies energy to a circuit. Active elements have the ability to electrically control electron flow. 

Examples:

  • Voltage sources
  • Current sources (e.g. DC current source)
  • Generators (such as alternators and DC generators)
  • All different types of transistors (such as bipolar junction transistors, MOSFETS, FETs and JFET)
  • Diodes (such as Zener diodes, photodiodes, Schottky diodes, and LEDs)

Passive Components:

              A passive component is a component which can only receive energy, which it can either dissipate, absorb or store it in an electric field or a magnetic field. Passive elements do not need any form of electrical power to operate.

Examples:

  • Resistors
  • Inductors
  • Capacitors
  • Transformers
Resistors:
                Resistor is a passive electrical component that reduces the electric current. In an electrical circuit schematics, the resistor marked with the letter R.

                The resistor's ability to reduce the flow of electric current is called resistance. Resistance is measured in the unit called ohms, and it is abbreviated with the Greek symbol Ω (omega).

                Symbolic representation of resitor is shown below

                                            

Inductors:
                 An inductor is a passive component that is used to store energy in the form of magnetic field when electricity is applied to it. One of the key properties of an inductor is that it opposes any change in the amount of current flowing through it. Whenever the current across inductor changes it either acquires charge or loses the charge in order to equalize the current passing through it.

                Inductance is the property of the coil in which the emf is induced because of the variation of flux. The unit of inductance is henry (H) and it is denoted by the symbol L. The symbol for inductance is a series of coils as shown below

                                                

Capacitors:

                The capacitor is a device in which electrical energy can be stored. It is an arrangement of two-conductor separated by an insulating medium. The non-conductive region can either be an electric insulator or vacuum such as glass, paper, air or semi-conductor called as a dielectric.

                Capacitance is defined as the capability of an element to store electric charge. The unit of capacitance is Farad (F) and it is denoted by the symbol C. The symbol for capacitor is shown below

                                                      


Voltage source:

                 A voltage source is a two-terminal device whose voltage at any instant of time is constant and is independent of the current drawn from it. Such a voltage source is called an Ideal Voltage Source and have zero internal resistance. Practically an ideal voltage source cannot be obtained.

             Sources having some amount of internal resistances are known as Practical Voltage Source. Due to this internal resistance; voltage drop takes place, and it causes the terminal voltage to reduce. The smaller is the internal resistance (r) of a voltage source, the more closer it is to an Ideal Source.

The symbolic representation of the ideal and practical voltage source is shown below.

Current source:

                 The current sources are further categorised as Ideal and Practical current source. An ideal current source is a two-terminal circuit element which supplies the same current to any load resistance connected across its terminals. It is important to keep in mind that the current supplied by the current source is independent of the voltage of source terminals. It has infinite resistance.

                   A practical current source is represented as an ideal current source connected with the resistance in parallel. The symbolic representation is shown below:


Independent sources:
                 Independent sources are that which does not depend on any other quantity in the circuit. They are two-terminal devices and has a constant value, i.e. the voltage across the two terminals remains constant irrespective of all circuit conditions.

             The strength of voltage or current is not changed by any variation in the connected network the source is said to be either independent voltage or independent current source. In this, the value of voltage or current is fixed and is not adjustable.

Dependent sources:

                 The sources whose output voltage or current is not fixed but depends on the voltage or current in another part of the circuit is called Dependent or Controlled source. They are four-terminal devices.

                 When the strength of voltage or current changes in the source for any change in the connected network, they are called dependent sources. The dependent sources are represented by a diamond shape.












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