Electronics components and what they do

In this article, you will learn about electronics components, their type and applications of electronics components used in electronics projects. I have discussed in detail types and use of electronics components in electronics projects.  Circuit symbols of electronics symbols are also given in this article. After reading this article you must know about almost every basic electronics component and their use in electronics projects. List of basic electronics components is given below :

Electronics components

Electronics components

List of electronics components :

  1. Resistor
  2. capacitors
  3. diodes
  4. Light emitting diodes
  5. switches
  6. Transistors
  7. Wire connections
  8. power supplies
  9. fuse
  10. transformer
  11. Microphone
  12. Earphone
  13. Loud speaker
  14. piezo transducers
  15. amplifier
  16. Antenna
  17. volt meter
  18. Ammeter
  19. galvanometer
  20. ohm meter
  21. oscilloscope
  22. lamp
  23. heater
  24. motor
  25. bell
  26. inductor

List of electronics components I have explained in this article is given above. I have explained types of these electronics components also. Let’s start with resistor.

Resistor :

resistor symbol

resistor symbol

Resistor oppose the current to flow in circuit . For example, a resistor is placed in series with a light emitting diode to limit the current to flow from light emitting diode. Resistors are either connected in series or parallel connection. Resistors can be connected in any form without risk of damage. They damage only with extra heat. Resistance is measured in  ohm and symbol for ohm is Ω .  Resistance values starts from 1Ω and go upto mega ohms. Resistance values are shown using colour code. As different colours are shown in resistor symbol. Each colour represents a number which is used to calculate value of resistor. Each resistor have four colourtable for colour code bands and each colour band have specific number assigned to it as shown in table. Follow the procedure the following procedure to calculate value of resistor using colour code.

  • First colour band represent first digit
  • Second colour band represent second digit
  • Third colour band represent number of zeros
  • Fourth colour band provides the tolerance of the resistor which may be ±5 %.

By following above given four steps, one can easily calculate value of resistor without using any measurement meter. Ohm meters are also available which can be used to measure resistance of resistor.

Types of resistors :

Rheostat :  It is a type of variable resistor with two contacts. It is used to limit current in circuit.For example rheostat is used control lamp brightness, speed control of dc motor and it is also in timing circuits to control the flow charges to capacitor. Circuit symbol of rheostat is given below

rheosate symbol Potentiometer : It is a variable resistor with three contacts. It is used to control voltage. It is used in many an application where we need to convert current into voltage form. Potentiometer is used as a transducers to convert one physical force into voltage form in angle of control spindle. Circuit symbol of potentiometer is given below:

potentiometer symbol

potentiometer symbol

Preset variable resistor :

It is another type of variable resistor. As it name suggest it is pre set variable resistor. It is designed to set when circuit is made. It is adjusted with the help of screw driver. Cost of preset resistor is less than other type of variable resistor. Therefore it is mostly used in electronics projects  to make project more economical. Circuit symbol of preset resistor is given below :

preset resistor symbol

preset resistor symbol

Capacitors :

Capacitors are used to store electrical charge through electric filed. Capacitors store charge between two plates of capacitor. I am not going to discuss working and internal construction of capacitor, because it needs extra article to discuss it completely.  Capacitor is also used in timing circuits along with resistors. There are enormous applications of capacitors in electrical field.  For example, capacitors are used in filter circuits due to its feature to pass AC signal and block DC signal.Generally capacitors are of two types. Polar capacitor and non polar capacitor.



Capacitance is measured in farad and denoted by F. one farad 1F is very large value of capacitance. Therefore capacitance is represented in small prefixes. Usually three prefixes are used to denote value of capacitors micro (υ) , nano (n) and pico (p) .

Types of capacitors :

Polar capacitor :

Polarized capacitor is usually used in DC circuit. It is used to store electrical energy. This type of capacitor have polarity which means it should be connected properly with respective to positive and negative polarity. It is used in timing circuits, filters circuit to block DC and to pass AC. Circuit symbol of  polar capacitor is given below:

polar capacitor

polar capacitor

Non polar capacitor :

Non polarized capacitors are used in AC circuits. It is used to remove harmonics from AC signals and allow only specific frequency signals to pass into circuit. Circuit symbol of non polar capacitor is given below:

non polar capacitor

non polar capacitor

variable capacitor :

Variable capacitor as it name suggests is used to get variable capacitance. It is used in radio tuner circuit to change the frequency of channel. In radio when you move the knob , you actually changing the capacitance. Change in capacitance ,change the frequency modulation of circuit with respect to required channel you want to tune in.Circuit symbol of variable  polar capacitor is given below:

variable capacitor

variable capacitor

trimmer capacitor :

Just like a preset resistor, trimmer capacitor is operated with a small screw driver. Is is also set during circuit designing. Its value is adjusted before using it in circuit. Circuit sybmol of trimmer polar capacitor is given below:

trimmer capacitor

trimmer capacitor

Diodes :

Diodes are electronics devices which allow current o flow only in one direction. Practical diode and circuit symbol of diode is shown below. Arrow of circuit shows the direction of current flow. Arrow with vertical side is called cathode and other one is called anode. Figure below also shows circuit symbol of zener diode. I will explain it later. Diods have many applications in electrical and electronics circuits. For example rectifier diode is used to convert AC signal into DC in rectification. Zener diode is used in voltage regulator circuit. Diodes are also used as free wheeling diodes. Similarly



Type of diodes :

zener diode :

Zener diode is special purpose semi condutor diode. It is used to mantain fixed voltage in regulated power supplies.

zener diode

zener diode

Light emitting diode :

Light emitting diode is a type of transducers which converts electrical energy into light energy.

light emitting diode

light emitting diode

photodiode :

It is a special type of diode which converts light energy into electrical energy. same process is used in solar cells.

photo diode

photo diode


Push switch:

This is a simple push button it permits current flow only in one direction when button is pressed. It has many applications like electronics circuits, door bells, led lights charging lights and many others. Circuit of push switch is shown below:

Push to break switch:

It also allow current to flow only in one direction. But it works opposite to push switch. It stops current to flow when button is pressed. It is used in applications where we want continues power to circuit until button is not pressed. Circuit symbol of push to break switch is shown below:

Single pole single through switch (SPST):

It also allow current to flow in one direction but it have two states, on state and off state. SPST switches are used in domestic and industrial switch boards. Symbol of SPST switch is shown below:

Single pole double through switch (SPDT):

As it name suggest single pole double through switch connects with one phase and allow current to flow in one of two possible circuits or routes. As shown in figure either upper or lower route can be connected to single phase supply.

Double pole single through switch (DPST):

It allows current o flow only in one possible route according to respective pole. It can be used to switch main electric supply it can use used to isolate neutral and live connections of main power supply. Circuit symbol of DPST switch is shown below:

Double pole double through switch:

It is also called reversing switch. It can be used to reverse direction of motor. It also have central off position. DPDT circuit symbol is shown below:


It is electro mechanical switch which operate with external power source. It is used to operate high power or high voltage circuits with low power dc circuits. It can be either normally closed or normally open. Its all three terminals are shown below:


Three types of transistors are used in electronics projects. Description of each of them is given below:

NPN transistor:

NPN transistor used in many electronics circuits. It is used as a switch, amplifier and current amplifier and also in oscillator circuits. Circuit symbol of NPN transistor is shown below:

PNP transistor:

PNP transistor has same applications like NPN transistor. But the direction of current flow is opposite in PNP transistor. PNP and NPN transistor together also used to make Darlington pair and totem pole configuration.

Photo transistor:

It is light operating transistor. Photo transistor operates with intensity of light. Whenever amount of light fall on base of transistor, it turns on. Photo transistor has many applications in automatic street light control circuit and auto intensity control of street lights.

Wiring and electrical connections in electronics circuits:

It is important to understand wiring connection to understand electrical diagrams. Following symbols are mainly used for wiring connections in electrical circuits.


It is just a line which is used to represent path of current. It is shown below:


As shown in figure below, sold bold circle is used to represent one of more connection of wires. In other words, a point where two or more wires connect with each other.

Not connected point or wires crossing:

In electrical electronics circuit wires crossing symbol shows not connected point. Wires crossing symbol is shown below:

Power supplies:

Following types of powers supplies are used in electronics and electrical projects.


Circuit symbol of cell is shown below. Larger terminal shows positive terminal of cell and smaller terminal shows negative terminal of cell. Many people used to call battery to cell. But in electrical battery consists of two or more cells.


Electrical symbol of battery is shown below. As I have mentioned earlier, battery consists of two or more cells. Battery supplies DC electrical energy.

DC supply:

DC power supply supplies dc current which flows in one direction only. DC power supply can be made from AC power supply or using batteries. Circuit symbol of DC power supply is shown below:

AC supply:

AC power supply alternating current. Circuit symbol of AC power supply is shown below:


Fuse is very important components of electrical circuits. It provides protection to circuit in case of over current or short circuit in electronics circuits. Fuse melts when excessive current flows through circuit.


Transformer is mainly used in AC circuits. But it is also used in dc power supplies to step down voltage. Transformer can be used either as step down or step up transformer. Transformer used electromagnetic induction to transfer energy from one circuit to another. Circuit symbol of transformer is shown below:

Audio and Radio devices:


It is a transducer which converts sounds into electrical energy. Its circuit symbol is shown below:


It is a transducer which converts electrical energy into sound. Circuit symbol is shown below:

Loud Speaker:

It is also used to convert electrical energy into sound with high amplification ability.

Piezo transducer:

Piezo transducer converts force (stress) into electrical energy.


Amplifier has many applications in electrical and electronics projects. Amplifiers are used to amplify voltage, current and signals level. Circuit symbol of amplifier is shown below.


Antenna is a device which is used to transmit and receive data through wireless communication. Antenna is used to receive and transmit radio waves. Circuit symbol of antenna is shown below.


Output devices:

Followings are the list of electronics output devices used in electronics projects:


Lamp is a transducer which converts electrical energy into light energy.


 Heater is a kind of transducer which used to convert electrical energy into heat.


Motor converts electrical energy into mechanical energy.


Buzzer converts electrical energy into to beep sound.


Inductor is a coil of wire which stores a magnetic energy when current passes through it.

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