An Electronic Device,in which the flow of Electrons is through a Vaccum is known as Vaccum Tube.A Vaccum Tube usually contains a Cathode which is called as Electron Emitter,an Anode which is called as plate (which is electron Collector) and one or more Electrodes called as Grids,for controlling the flow of Electrons between the Cathode and Anode.These Electrodes are housed in highly evacuated glass envelope.The Anode is held at Positive Potential with respect to Cathode,so that Emitted Electrons are attracted to Anode to provide Current in Vaccum Tube.The application of Vaccum Tubes are so varied

The substance used for Electron Emission is known as an Emitter.An Emitter should have the following Properties.01)High Melting Point:-As Electron Emission takes place at very High Temperatures,therefore,the substance used as Emitter should have High Melting Point.02)Low Work Function:-The substance selected as an Emitter should have Low Work Function so that Electron Emission takes palce by applying small amount of Heat Energy. 03)High

The substance used for Electron Emission is known as Emitter or Cathode.The Cathode is heated in an evacuated space to emit Electrons.As Cathode is sealed in Vaccum,therefore,the most convenient way to heat it is Electrically.The heating processes may be done by two methods.The Thermionic Cathode are devided into two types,01)Directly Heated Cathode02)Indirectly Heated Cathode01)Directly Heated Cathode:-In

The Branch of Engineering which deals with Current Conduction through a Vaccume or Gas or Semiconductor is known as Electronics. Electronics mainly deals with Electronics Devices and their utilization.Such Devices have valuable properties which enable them to function and behave as the friend of Human today. Electronics has gained much importance due to its numerous application in Industry.The Electronics Devices are capable of performing various functions.Out of that the main functions are as below.01)Amplification:-The

At Room Temperature,the Thermal Energy in the Conductor is adequate to break the bonds of the Valence Electrons and leave them unattached to any oneNucleus.These Unbound Electrons moves at random within the Conductor and are known as Free Electrons. If an Electric Field is applied across the Conductor,these Free Electrons move through the Conductor in an orderly manner,thus constituting Electric Current.Many Electronic Devices depend for their operation on the movement of Electrons in an evacuated space.For this purpose,the Free Electrons must be ejected from the surface of Metallic Conductor

From my previous post,you come to know about "Emission of Electrons".This Electron Emission can be classified in four different types.The details about thatfour types are as below.The External Energy which is used for Emission of Electrons,may come from variety of sources such as Heat Energy,Energy stored in Electric Field,LightEnergy or Kinetric Energy of the Electric Charges Bombarding the Metal Surface.Accordingly,there are four principle methods of obtaining Electron Emission from the Surface of Metal.01)Secondary

Thermistor is a means of a term "Thermal Resistars".Thermistors are generally made from Semi-Conductor Materials.Most Thermistors have Negative Coefficient of Temperature Resistance i.e.Their Resistance decrease with increase in Temperature.The Negative Temperature Coefficient of Resistance can be large as several percent per Degree Celcius.This allows the Thermistor Circuits to detect very small changes in Temperature which could not be observed with a Thermocouple.Thermistors are widely used in applications which involves Measurments in the range of minus 60 degree centigrate to 15 degree

A Hygrometer measures the Value of Humidity Directly.Generally,the output of Hygrometer is used to indicate Relative Humidity. Several Material exhibit changes in Electric Properties that are caused by Humidity.These are frequently used in Transducers that are designed and Calibrated to read Relative Humidity Directly.01)Resistive Hygrometer:-Some Hygroscopic Salts exhibit a change in Resistivity with Humidity.The most common is Lithium Chloride.This,with a Binder may be coated on a wire or on Electrodes.Resulting Resistance changes cover a wide range for example 10 rase to four to 10 rase to

The Liquid Levels can be measure by different methods but following two are more important from the subject point of view.01)Electrical Methods:-The Direct Conversion to Liquid Level position to Electrical Signal is used in many instances.The measurements is generally done by two conversions,so that the Liquid Level is determined indirectly.The first conversion usually is Liquid Level to a Displacement through a Float in a Liquid or a Spring Loaded Plate in contact with the surface in the case of Granular Solids.This

In order to overcome some of the diffculties,A.C.Tachometer Generators are used.The Tachometer has Rotating Magnet which may be either Permanent Magnet or an Electromagnet.The Coil is wound on the Stator and therefore the problems associated with Commutator (as in D.C.Tachometer) are absent.The rotation of the Magnet causes an E.M.F to be induced in the Stator Coil.The Amplitude and the Frequency of this E.M.F. are both proportional to the speed of Rotation.Thus either Amplitude or Frequency of induced voltage may be used as a measured of Rotational Speed.The Output Voltage of A.C.Tachometer Generators