Basically there are two categories of electronic devices. They are active devices and passive devices.

Active devices: 

Active devices need external energy to operate and it produces energy in the form of voltage or current to the circuit. Active components are
  • Diodes
  • Transistors
  • Vacuum tubes
  • Integrated circuits

Passive devices:

A passive device doesn’t need external energy or source to function. It stores energy in the form of voltage or current or dissipates the energy. The passive components are
  • Resistors
  • Capacitors
  • Inductors 

Let’s see in detail about the basic electronic devices.

DIODES:

A diode is a two terminal electronic component which conducts current in one direction. The two terminals are anode and cathode. When positive voltage is given to the anode and cathode negative voltage the free electrons from cathode flow toward the anode and thus the current flows. When they are are reversely connected they do not allow current to flow. when Mostly diodes are made up of semiconductor materials such as silicon, germanium or selenium.


Types of diodes
Types of diodes

TRANSISTOR:

Transistor  is a semiconductor device which acts like a switch. It has three terminals . when the voltage is applied to one of the terminal the current or voltage between the other terminals or amplified ,oscillated or switched. It is like the faucet which controls the flow of water.


Transistors
Transistors

Types of transistors
Types of transistors




VACUUM TUBES:

The vacuum tube is a tube in which gas is removed and thus vacuum is created. The basic working principle of vacuum tubes is thermionic emission. When you heat up a metal the thermal energy makes some electrons loose. The vacuum tube consisted of two electrodes a cathode and an anode placed on either side of the tube. When the cathode is heated up due to thermionic emission the electrons are loosened and while applying positive voltage to the anode, these negatively charged electrons (e-) are attracted towards anode. By creating vacuum that is by removing the gas the path is made clear for the electrons to move from cathode to anode. Thus current is created.


Vacuum tubes
Vacuum tubes

INTEGRATED CIRCUITS:

Integrated circuits is a set of electronic circuits on one small piece(chip) of semiconductor material normally silicon. An integrated circuit can hold transistors, resistors and capacitors . These integrated circuits can perform calculations and store data using either digital or analog technology. 

Integrated circuits
Integrated circuits

Types of Integrated Circuits
Types of Integrated Circuits

RESISTORS: 

As the name suggests Resistor  it controls the flow of current. The effect of resistor is called resistance. It also regulates or sets the flow of electrons the conductive material which they are made of.  It is measured in unit called ohms(symbol Ω).