ELECTRONIC DEVICES: INTRODUCTION

  watch the presentation in youtube channel also. 

Youtube channel name:DrMBJ

What is Electronics?

• Electronics is the branch of science

• deals with the study of flow and control of electrons 

• study of behavior of electrons and their effects in vacuums, gases, and semiconductors

• Devices (electronic components) for control of such electrons.

    What sets electronic circuits different from electrical circuits is its ability to make decisions, process information, and interpret a signal or instruction to perform a task.

Development of Electronic Devices:

• William Gilbert is the one coined the word electricus, while on his pioneering research on magnetism and static electricity.

• Every electronics engineer had encountered Robert Kirchhoff, famous for the Kirchhoff’s Laws

• With a record of 1,093 patents which comprise key and minor innovations(though early inventions was never patented), Thomas Alva Edison is perhaps the most celebrated inventor in American history

• The inventor of the oscillation diode valve or vacuum tube, John Ambrose Fleming is the one who set the benchmark for modern electronics, which why he is regarded as the father of modern electronics

• Lee De Forest who invented the Audion vacuum tube, which made live radio broadcasting possible before the invention of the transistor

• Walter Schottky who laid work in solid-state physics and electronics, discovered an irregularity in the emission of thermions

• Philo Taylor Farnsworth is the man who invented the electronic television, at only age 21.

• The transistor era began with the junction transistor invention in 1948; this particular invention got a Nobel Prize.William B. Shockley worked on semiconductor to control and amplify electronic signals, with John Bardeen and Walter Brattain.

• The subsequent years (1958 to 1975) witnessed the invention of the integrated circuits (ICs) that drastically changed the electronic circuits’ nature as the entire electronic circuit got integrated on a single chip JFETS and MOSFETs that were developed during 1951 to 1958 by improving the device designing process and by making more reliable and powerful transistor

• Digital integrated circuits were yet another robust IC development that changed the overall architecture of computer

• Later digital ICs employed PMOS, NMOS, and CMOS fabrication design technologies

EXPERIMENT : CONVERSION OF A GALVANOMETER INTO VOLTMETER

 AIM 

    To convert a given galvanometer into voltmeter of desired ranges and to calibrate it. 

APPARATUS USED 

    Galvanometer, voltmeter, connection wires, shunt resistance, key

WORKING PRINCIPLE 

    A galvanometer can be converted into voltmeter by connecting a high  resistance (shunt) wire series to it

Converting a galvanometer into a voltmeter

What is a voltmeter?

    Voltmeter is an instrument used to measure potential difference between the two ends of a current carrying conductor.

THEORY:

     A galvanometer can directly measure small potential differences only. To measure high potential differences, that is, to convert the galvanometer as voltmeter, some modifications has to be done in the galvanometer.

     Suppose to convert the galvanometer that can measure the potential difference up to V, the range of the voltmeter is 0 – V. For this, a suitable high resistance is connected in series with the galvanometer such that when a potential difference of V is applied, only a current Ig passes through the galvanometer as shown in the figure 1. 

Fig 1: Conversion of galvanometer into voltmeter

• A galvanometer can be converted in to a voltmeter by connecting a high resistance in series with it. 

• The scale is calibrated in volt. 

• The value of the resistance connected in series decides the range of the voltmeter.

FORMULA USED

To convert a galvanometer into a voltmeter of desired ranges, the resistance to be connected in series to it is given by.

  i) Shunt resistance, S = [V / I g  ] -G             --------> equation1

                      

                           Here,    

                                        S - shunt resistance in ohms 

                                        G - Resistance of galvanometer in Ohms. 

                                        I g - Current for full scale deflection in galvanometer in mA.

                                         v - Desired range of voltmeter in v. 

            ii) Ig is calculated using the equation,

  Ig = nk                         --------> equation2

                Where

                                 n - the number of divisions on the galvanometer (30 div)

                                 k - the figure of merit of galvanometer

            The figure of merit of a galvanometer is defined as the current required in producing a unit                     deflection in the scale of the galvanometer.  It is represented by the symbol k

                iii) K is given by the equation,

                                         K = E/ (P+Q) *P/d *1/G                --------> equation3

                        Where

                                        E - e.m.f. of the cell 

                                        G - deflection produced with resistance R

PROCEDURE

 Determination of Galvanometer Resistance (G) : 

Fig 2: Circuit diagram to find G

1. Take the circuit connection of figure in order to determine the resistance of the galvanometer by half deflection method. 

2. Introduce some high resistance Q (in the range 980 -999 ohm) and P (1-20 ohm)in the resistance box such that P +Q=1000 ohm.

3.If the deflection in the galvanometer goes out of scale bring it within the scale by adjusting the value of P,Q . 

4. Now, Increase the value of R ohm  in  resistance box. Adjust the value such that the deflection in galvanometer becomes half of its previous value.

OBSERVATION

From equation3,  

    the calculated value of figure of merit of a galvanometer(k)=2.1 x 10^-5 ampere/div

Substituing k in equation2,

   

    Current for full scale deflection in galvanometer(Ig) = 630 x 10^-6 ampere

From equation1, 

    To convert a galvanometer into a voltmeter of desired ranges(say, 10V),  the value of resistance(S) to be connected in series = 15,798 ohm

                                                               

Fig
3: Calibration galvanometer into a voltmeter

Full deflection in the galvanometer ie., 30 divisions is equal to 10V.

Then, 1V=3 divisions in galvanometer.

RESULT

    The given galvanometer is successfully converted into a voltmeter