EMITTER, COLLECTOR AND BASE OF A TRANSISTOR

A transistor has three sections, The section on one side is Emitter, and the section on the opposite side is the collector.  The middle section is called the base.

Emitter:
The section on one side that supplies charge carriers (electrons) is called the emitter. The emitter is always forward biased with respect to base.

Collector:
The section on the other side that collects the charges is called the collector. the collector is always reverse biased.  Its function is to remove charges from its junction with base.

Base:
The middle section which forms two pn junctions between the emitter and collector is called the base.
The base emitter junction is forward biased and the base-collector junction is reverse biased.

TRASISTOR

When a third doped element is added to a crystal diode in such a way that two pin junctions are formed, the resulting device is known as transistor.

A transistor consists of two pn junctions formed by
sandwiching either p type or n type semiconductor between a pair of opposite types.

there are two types of transistors

1) n-p-n transistor
2) p-n-p transistor


A n-p-n transistor is composed of two n-type semiconductors separated by a thin section of p-type semiconductor. 

A p-n-p transistor is composed of  two p-type semiconductors separated by a thin section of n-type semi conductor.

In any transistor, there are two pn junctions.  therefore a transistor may be regarded as a combination of two diodes connected back to back.

There are three terminals in a transistor  1) Emitter
2)Collector    3) Base

WHAT IS A COLUMN, SHORT COLUMN, LONG COLUMN

Column:
A column is a vertical compression member.  A column is subjected to axial compressive loads.

Short Column:
When the ratio of effective length to the least lateral dimensions of the column is less than 12, then it is
called a short column.

(or)
When the ratio of effective length to the least radius of gyration is less than 45, then it is called a short column

Long Column:
When the ratio of effective length to the least radius of gyration is greater than 45, then it is called a long column.

A long column is subjected to bending moment in addition to direct compressive stress.

The load carrying capacity of a long column is less than a short column

The load carrying capacity of a long column depends upon slenderness ratio (slenderness ratio increases then the capacity of the column decreases)

WHAT IS FOREX, FOREIGN EXCHANGE MARKET

Foreign Exchange, simply called Forex
also called as currency market.  Simultaneous purchase and sale of one country's currency to
another country's currency.  in simple terms
buying of one currency and selling another currency at the same time.

The world currencies do not have a fixed exchange rates and they are always fluctuating.

Forex trading allows an investor to participate in profitable fluctuations of world currencies.

FREEZING OF LAYERS IN AUTOCAD

Freezing of a layer means it freezes the selected layer in all viewports, including the Model Tab.  You can freeze layer to speed up zoom, Pan and many other operations and to improve object selection performance, reduce regeneration time for complex drawings. 

Use Freeze option, if you want a layer to be invisible for long periods.  If you plan to switch visibility settings frequently, use the on/off setting to avoid regenerating the drawing. 

CUP AND CONE FRACTURE

Mild Steel specimen features with cup and cone fracture.  Cup and Cone fracture is the characteristic property of mild steel.

BENDING STRESS

Bending stresses are produced in beams due to bending moment.  The bending moment is also called as flexural stress or skin stress.  it is denoted by the letter "f".

                  M
         f  =  ____

                  Z

where  M= Bending moment
           Z=  Section Modulus ( I/Y)

SHEAR STRESS OR TANGENTIAL STRESS

when the Force acts tangential to the area of cross section it is called shear stress or tangential stress.  The stress produce by shear force is called shear stress or tangential stress.  shear stress is the ratio of shear force to shear area.

ZENER DIODE

A properly doped crystal diode which has a sharp breakdown voltage is known as zener diode.  A zener diode is like an ordinary diode except it is properly doped.   A zener diode is always reverse connected (reverse biased)  Zener diode has sharp breakdown voltage i.e zener voltage.

ZENER CURRENT, ZENER VOLTAGE

When the reverse bias on a crystal diode is increased, a critical voltage, called break down voltage is reached.  where the reverse current increases sharply to a high value.  The explanation for the breakdown region is given by C.Zener.  therefore breakdown voltage is called zener voltage and the sudden increase in current is known as zener current.
The breakdown or zener voltage depends upon the amount of doping.  If the diode is heavily doped, depletion layer will be thin and consequently the breakdown of the junction will occur at a lower reverse voltage.  A lightly doped diode has a higher break down voltage.

FILTER CIRCUITS

A Rectifier is required to produce pure D.C supply for using at various places in the electronic circuits.  However, the output of a rectifier has pulsating character.  It contains A.C and D.C components.  The A.C component is undesirable  and must kept away from the load.  To do so, a filter circuit is used which removes the A.C component and allows only the D.C component to reach the load.

A filter circuit is a device which removes the A.C component of rectification output but allows the D.C component to reach the load.

RIPPLE FACTOR

The output of a rectifier consists of a D.C component and an A.C component ( also known as Ripple)
The A.C component is undesirable and accounts for the pulsation in the rectifier output.  The effectiveness of a rectifier depends upon the magnitude of A.C component in the output.  The smaller this component, the more effective is the rectifier.

The ratio of r.m.s value of A.C component to the D.C component in the rectifier output is known as Ripple Factor.   Ripple factor is very important in deciding the effectiveness of a rectifier.

FULL WAVE RECTIFIER

In full wave rectification, current flows through the load in the same direction for both half-cycles of input A.C voltage.  This can be achieved with two diodes working alternatively.  For the positive half cycle of input voltage one diode supplies current to the load and for the negative half cycle the other diode does so, current being always in the same direction through load.  Therefore a full wave rectifier utilises both half cycles of input A.C voltage to produce the D.C output.

EFFICIENCY OF HALF WAVE RECTIFIER

The ratio of D.C power output to the applied input A.C power is known as Rectifier Efficiency.

HALF-WAVE RECTIFICATION

In Half-wave rectification, the Rectifier conducts current only during the positive half cycles of input A.C.Supply.  The negative half-cycles of A.C supply are suppressed.  i.e during negative half cycles no current is conducted and hence no voltage appears across the load.  Therefore current always flow in one direction (i.e D.C) through the load.

SEMI CONDUCTOR DIODE

A p-n junction is known as semi conductor diode or crystal diode.  The out standing property of a crystal diode to conduct current in one direction only permits it to be used as a rectifier.

P-N JUNCTION

p-n Junction conducts current easily when forward biased and practically no current flows when it is reverse biased.  This unilateral conduction characteristic of P-n junction is similar to that of a vacuum diode.

DISADVANTAGES OF HALF-WAVE RECTIFIER

Half-wave rectifier is seldom used in practice because
1) The rectification efficiency is low
2) The D.C output is small
3) Secondary transformer carries the rectified current, thus producing direct magnetisation of the transformer core.
4) Because of short heavy pulses of current, the heating of transformer winding is large compared to the current delivered.

RECTIFIER

Rectifier is an electronic device that converts alternating current into direct current is called rectifier.
A rectifier changes A.C into D.C by eliminating the negative half cycles of the alternating voltage.  It may work as a switch that closes a load circuit during the positive half cycle of A.C supply and opens the circuit during the negative half cycle.  Therefore a rectifier provides one-way path for electric current.

VACUUM TUBE

Vaccum Tube is an electronic device in which the flow of electrons is through a vacuum is known as vacuum tube.  A vacuum tube usually contains a cathode which is the electron emitter, an anode(plate) which is the electron collector and one or more electrodes (called grids) for controlling the flow of electrons between cathode and plate.  These electrodes are housed in a highly evacuated glass envelope.  The plate is held at positive terminal with respect to cathode so that emitted electrons are attracted to plate to provide current in vaccum.

THEVENIN'S THEOREM

Thevenin's Theorem is used to find a particular branch current in a circuit as the resistance of that branch is varied while all other resistances and voltage sources remain constant.

"Any two terminal network containing a number of e.m.f sources and resistances can be replaced by an equivalent series circuit having a voltage source Va in series with a resistnce Ra."

where Va=voltage between two terminals
          Ra=Resistance between two terminals

AMPLIFICATION

The process of raising the strength of a weak signal is known as amplification.  Electronic devices can accomplish the job of amplification are known as amplifier.

RECTIFICATION

The conversion of A.C into D.C is called Rectification.

ELECTRONICS

The branch of engineering which deals with current conduction through a vaccum or gas or semi conductor is known as Electronics. An Electronic device is that in which current flows through a vacuum or gas or semi conductor.

STEPPER MOTORS

The Stepper Motor is a form of synchronous motor which is designed to rotate a specific number of degrees for each electrical pulse received by its control unit.  The stepper motor is used in digital control systems where the motor receives open loop commands as a train of pulses to turn a shaft or move a plate by a specific distance.  A typical application for the motor is positioning a work table in two dimensions for automatic drilling according to programme.

SERIES MOTORS

A Series Motor has has ability to run on either alternating or direct current.

RECTIFIER

Rectifier circuit is used to convert A.C Current into D.C. Rectifier is a circuit assembled from diodes and thyristors.  Which supplies direct current to the armature and field to and field of the motor from the A.C supply line.

INVERTERS

Inverters are used to transfer energy from a dc source to an ac load of arbitrary frequency and phase.  Inverters are used to supply uninterrupted ac power to computers, house hold appliances and to convert energy between ac and dc from at the terminals of high voltage dc power transmission systems.

INDUCTION MOTOR

Induction Motor,  a motor has two windings, stator winding and rotor winding. An alternating current is supplied to the stator winding directly and to the rotor winding by induction from the stator.  Polyphase stator and rotor currents create balanced stator and rotor component mmf waves of constant amplitude rotating in the air gap at synchronous speed and therefore stationary with respect to each other regardless of the mechanical speed of the rotor.  The resultant of these mmfs create the resultant air-gap flux density wave.  Interaction of the flux wave and the rotor mmf wave gives rise to torque.  

LOGARITHMIC MEAN TEMPERATURE DIFFERENCE (LMTD)

Logarithmic mean temperature difference is the ratio of the temperature rise to the Napierian logarithm of the ratio of initial temperature difference to the terminal temperature difference.

DIFFERENCE BETWEEN TRUE SIZE AND ACTUAL SIZE

True Size:
It is the theoretical size of a dimension, which is free from any errors of measurement.

Actual Size:
It is the value of size obtained through measurement with permissible measuring error.

HOW TO CREATE TITLE BLOCK IN MODEL SPACE OF AUTO CAD

Drawing in full scale brings up the problem of how to place a drawing sheet border and title block around a model that may be a hundred feet wide.  The answer is simple create title block full size, then insert it as a block in your drawing using the inverse of the scale that you would use to plot the drawing.

PAPER SPACE SCALING IN AUTO CAD

Paper space in Auto Cad, the place where we arrange our drawing work to get print out.  In general we finish our drawing in model space, and switch to paper space in order take print out.  In paper space to set scale, use "Properties" command, and select the view port, then change the value of scale as required.
We can also set the paper space scaling by using Zoom/xp ( zoom/scale).

COMPOSING A TITLE BLOCK IN MODEL SPACE IN AUTO CAD

Drawing in  full scale brings up the problem of how to
place a drawing sheet border and title block around a model that may be a hundred feet wide.  The answer is simple create title block full size, then insert it as a block in your drawing using the inverse of the scale that you would use to plot the drawing.

HYSTERESIS

It is the difference between the indications of a measuring instrument when the same value of the measured quantity is reached by increasing or decreasing that quantity. This phenomenon of hysteresis is due to the presence of dry friction as well as to the properties of elastic elements.

Hysteresis is particularly noted in instruments having elastic elements. This phenomenon of hysteresis in materials is due to the presence of internal stresses.  It can be reduced considerably by proper heat treatment.

USES OF XREF'S IN AUTO CAD

Xref's are like ghost images of other files.
When several people are working on different parts of drawing, these parts can be incorporated into one master drawing as Xref's. Use this command "xref" to make a file external reference into your drawing.

If you want to make your xref data a permanent part of your drawing, just use "bind" option to make the particular drawing as permanent block in the existing
drawing. Use "reload" option to reload the external reference.

PARAMETRIC MODELING

It is a nature of 3D Modeling software package.
It makes easier to use the standard properties or parameters to represent a shape and size at any instant.  You can alter shape and size of the object with ease.  There are more no. of 3D software packages that represent the property of parametric modeling.  Example: Catia, Pro-E, Solid Works etc.,

USE OF OOPS COMMAND IN AUTO CAD

"OOPS" command restores objects erased by the last ERASE command.  You can also use OOPS command after Block or Wblock to restore the objects that are erased when a block is created. You cannot use OOPS to restore objects on a layer that has been removed with the PURGE command.

ADVANTAGE OF SHUNT MOTOR

The major advantage of shunt motor is its ease of speed control. With the use of rheostat in the shunt field circuit, the field current and flux per pole may be varied at will, and variation of flux causes the inverse variation of speed to maintain counter emf approximately equal to the impressed terminal voltage.  A maximum speed range of about 4 or 5 to 1 may be obtained by this method.  By variation of impressed armature voltage, very wide speed ranges may be obtained.

DEMAT ACCOUNT

Demat Account means a dematerialised account to trade in listed stocks or debentures in india in electronic form, as per the guidelines of the SEBI (Securities and Exchange Board of India) investor needs to open a Demat Account.

Instead of physical possession of various Certificates of shares and securities, these shares and Securities are held electronically in a Demat Account. Transfers or purchases of securities can be initiated from this demat account.

SMALL WORLD - A GIS SOFTWARE

SMALL WORLD is a Software related to Geographical Information Systems (GIS). Small World is the brand name of GIS software solutions provided by GE Energy.

"Small World" produces geo spatial solutions for companies with complex network asset management problems - electrical, telecommunications, gas, water and public authorities.

"SMALL WORLD WATER OFFICE SOFTWARE"

GE Energy's New "Small World Water Office
Software Solution" for Water Supply and Drainage Networks.

It is a suite of data models,applications and integration products designed to help water supply and drainage utilities to meet their current and future spatial asset management needs.

AUTO CAD

AUTO CAD,  is a powerful 2D, 3D design software.
it has a reputation world wide for its outstanding 
capability in  2D drawings as well as 3D modeling.

there are several industry specific packages like
Auto Cad -Mechanical, Auto Cad-Electrical 
Auto Cad -Plant 3D etc.,

Auto Cad is developed by Auto Desk Inc.,

Auto Cad is widely used in Manufacturing, Design
Services, Process design for developing 2D detailed
drawings and P & ID's(process and Instrumentation diagrams).

CATIA

CATIA, its a 3D Modeling Software widely used in manufacturing, Aerospace, Railways, ship building etc.,

Catia, is developed by Dassault systems.
it has reputation for its high end technology and
thus widely used by reputed industries for their research and development.

Earlier versions of Catia are  V4, V5, and now V6

It covers  part modeling, assembly modeling, surface modeling, sheet metal modeling and many more platforms (ex:piping).