Questions and Answers on electronics/instrumentation

Questions and Answers on
  electronics/instrumentation   Q. 1 Which is the negatively charged particle of an atom?

Ans:-A electron is the called negatively charged particle of an atom. 

Q. 2 What is Electron charge & mass?
 Ans:-  the charge of electron is 1.6 x 10 ^-19 C and  Mass of electron is 9.1 x 10 ^-31 kg.

Q. 3 What is  called the electric current?

Ans:- The flow of electrons in the conductor is called the electric current .

Q.4 What are  called the conductors?

Ans:- The Substances which allow electric current to flow them, are called conductors. 

Q.5 What are called the insulators ( bad conductors)?

Ans:- those Substances ,which do not allow electric current to flow them,its are called insulators.

Q6 what are the particles of an atom?

Ans:-The particles of an atom are as  neutron,electron,and proton.

Q.7 What are radio waves, Write the uses of radio waves?

Ans:- Radio waves are electromagnetic waves ,and its wavelengths greater than 0.1m.

Radio waves are used in communication systems including radars, TV, satellites and radio broadcasting.

Q.8 What do you understand by‘electronics’?

Ans:- Electronics is a field of physics and engineering  dealing with the design and application

of devices, usually electronic devices.

Q.9 write any four electronic devices.

Ans:- T.V., radio, microprocessors and digital computers are four electronic devices

Q.10 Mention the locations influenced by electronics.

Ans:- Electronics has influenced the locations such as  defense, industry ,entertainment,medical science and   communication,

Q.11 What are the most recent advances in eh field of electronics

Ans:-  In electronics the most recent advances are includes digital circuits, micro processors, digital computers, opto-electronics, laser technology and so on

Q.12 What are semiconductors? can you sagest any example?

Ans:- A Semiconductors are the material whose conductivity lies in between that of conductors and insulators.

as we can say  Silicon, Germanium, are the example for that

Q.13 How many electrons are there in the outermost shell of atom of silicon?

Ans:-  Four electrons in the outermost shell of an atom of silicon.

Q.14.  define‘hole’?

Ans:- When an electron is removed from a covalent bond, it leaves a opening(vacancy or blank space) equivalent to positive charge. It is called a hole, an electron from a neighboring atom, can drop into this vacancy, leaving the neighbor with a vacancy.

In the way, the vacancy called a hole can move and serve as an additional charge carrier.

Q.15.What are difference between intrinsic and extrinsic semiconductors?

Ans:- whose conductivity is due to equal number of holes and electrons present is

called intrinsic semiconductor (A pure semiconductor)

and whose conductivity is enhanced by the addition of the minute traces of the impurities

( other elements) called dopants, is called extrinsic semiconductor

Q.16. What is called the doping ?

Ans:- doping can say as the conductivity of semiconductors can be enhanced by the addition of other element(impurities)called dopants. The process of adding dopants is called doping and the resulting

semiconductor is called doped semiconductor or extrinsic semiconductor.

Q17. what are  the types of extrinsic semiconductors and uses?

Ans:- A extrinsic semiconductors ,we can say two types of  depending upon the types or impurities.

it can  classified as (a) N type semiconductors and (b) P type semiconductors.

A extrinsic semiconductors are used in the manufacture of  transistors and diodes.

Q.18. what are the difference between ‘n’ type ‘p’ type semiconductors.

Ans:- P- type semiconductors; small amount of pentavalent impurity for example antimony (or arsenic

or phosphorous), is introduced into the crystal of germanium, in this four out of five electrons of each impurity atom

enter into bonds with the nearest germanium atoms, to form covalent bonds and the fifth electron is set free.

therefore,the free electrons act as current carriers.

 semiconductors "n"- type:  Trivalent impurity like boron, indium, gallium is introduced into a germanium crystal, each impurity atoms takes away one electron from the neighboring germanium atoms can fill up these holes and there will be apparent motion of holes,holes act as electrons from the semiconductor and the semiconductor becomes a P- type semiconductor.

Q.19. What are the name two pentavalent impurities.

Ans:-  pentavalent impurities are as  Arsenic,Antimony, and phosphorus.

Q.20.What are the Name two trivalent impurities.

Ans:-  trivalent impurities are  Aluminium , indium, Gallium and boron .

Q.21.What is a semiconductor diode or junction diode,define it?

Ans:- When a donor impurity is added to one side and an acceptor impurity,it is added to the other side of pure semiconductor, the first side becomes n-type and other side becomes p-type. Thus a p-n junction is formed called Junction diode or a semiconductor diode.

Q.22. What do you understand as forward bias of a diode?

Ans:- When the positive terminal of cell is connected to p-side and the terminal of negative  to the n-side of a p-n junction,

it is said to be forward biases. The external voltage overcomes the junction potential and provides an easy path for the

flow of charge carriers across the junction. The flow of electrons from n to p and of holes from p to n, constitutes

a forward current (of the order of mA) from p to n. The device offers as a low resistance in that.

Q.23. What is mean reverse bias of a diode?

Ans:- When the positive terminal of a cell is connected to the n side and the negative terminal to the p side of a p-n junction it said to be reverse biased. In this case the charge of carriers repelled away from the junction and no current flows through the junction. we can say,The device offers high resistance

Q.24. State the important characteristics of diode, define it?

Ans:- in one direction only the p-n junction allows current to pass through prudentially, this action is called rectifying action and device is called ‘rectifier’.

Q.25. what are the applications of diode?

Ans:- A diode has a number of uses in view of rectifying action and current detection action.

a)  to convert AC into DC,Diode used for it (b) They are also used in voltage regulation systems

Q.26.what is the semiconductor device a transistor?

Ans:- The term ‘transistor’, it is a specially constructed three terminal semiconductor device

Q.27. Distinguish between transistors as p-n-p and n-p-n  ?

Ans:- in npn,  one region of  p type is sandwiched between two regions of n-type  is called npn transistor.

However in pnp transistor, a n-type region is sandwiched between two p-type regions.

Q.28. what are the Name the three regions of a transistor

Ans:- The middle region is called the and the two and regions are called emitter and the collector

Q.29. What are the functions of the three regions of a transistor?

Ans:- The function of the emitter is to emit electrons(in the case of npn transistor)or holes(in the case of pnp transistor)

into the base. The base controls the flow of charge carriers into the collector which collects them from the base.

Q.30. write the applications of a transistor?

Ans:- Transistor is used in (i) amplifier (ii) oscillator and (iii) switching circuits.

Q.31. can you say whats oscillator?

Ans:-  a device for producing electric oscillations of a desired frequency, called Oscillator. 

Q.32. write the types of transistors.

Ans:- Bipolar junction transistor, Field effect transistor (FET), Metal Oxide semiconductor Field effect transistor

(MOSFET)andJunction Effect Transistor Metal Semiconductor Fields effect Transistor are some of the other transistors.

Q.33.  write the technical means of communication?

Ans:- In basic sense, communication means transmission of information from one person to another In a technical sense, it refers to the sending, receiving and processing of information by electrical means,as Telegraph, telephone, radio, and television, radar so on are the technical means of communication

Q.34. write the different types of communication systems?

Ans:-  different type of communication as Telegraph, telephone, radio, television and radar etc aresystems

Q35 What is radio communication?

Ans:- Radio communication is called  the process of sending information  from one and receiving at another    place, without using connecting wires

Q.36. what are the Name of two major parts in radio broadcasting system?

Ans:- In radio broadcasting system namely a transmitter and a receiver

Q.37. what is the principle of a radio transmitter?

Ans:- The audio (sound) information is changed into corresponding electrical signal using a transducer. Transducer is a device that converts information energy to be transmitted into electrical signal. For sound transmission, the transducer is microphone (1) this signal called audio frequency (AF) signal, being weak, is amplified by a suitable amplifier called AF amplifier (2) As AF signals, have low energy, they can not be transmitted over long distances. Therefore radio waves of suitable frequency are generated in an RF oscillator (3) These radio waves are mixed with the amplified AF signal in the mixer stage (4) In this stage, modulated. The RF wave that carries the Af signal, is called carrier. Each transmitting station has a particular carrier frequency. The modulated signal is amplified using an RF amplifier (5) and then sent to the antenna (6) The antenna radiates the RF signal into space, in from of radio waves.

Q.38. what are the Name of Indian who constructed Radio Transmitter in1923.

Ans:- Dr. S.K. Mitra constructed Radio Transmitter in 1923

Q.40. What is a transducer?

Ans:- Transducer is a device that converts information energy to be transmitted into electrical signal

Q.41. What is the function of detector and loud speaker in a radio receiver?

Ans:- Detector or demodulator separates AF Signal from the carrier and loud speaker converts amplified AF

signal into sound (information) energy.

Q.42. What is the carrier frequency of i) AM ii) FM radio transmitter?

Ans: AM radio stations have carrier frequencies from about 530 to 1600 kHz, AM radio stations have much

carrier frequencies, between 88 to 108 MHz.

Q.43. What is the meaning of the word television?

Ans:- The combination of two words ‘tele’ and ‘vision’ literally means seeing at a distance.

Q.44. What is the process of television?

Ans:- The Television broadcasting is the process of transmission of transient visual image or picture of an actual or recorded scene, along with audio signal to  using radio waves.

Q.45. Write a short note on the principle of working of a television?

Ans:- A television transmitter works  similar as a radio transmitter. At the TV station, a pick up instrument like TV camera ,explores (scans) different portions of the picture or scene to be transmitted, in a particular order. The camera converts the variations in brightness in the various part into electrical impulses for that a photoelectric device is used as transducer. These electrical impulses constitute the video signal and these video signal is amplified and it used to amplitude modulate an RF carrier.

As we can say that a microphone is amplified of the sound picked up  and is used to frequency modulate an RF carrier (The frequency of this carrier is 5.5 MHz higher than that of the video carrier). Carrier frequencies range from about 40 MHz to MHz.in TV for various channels lie.

The two modulated carries are amplified and transmitted through the same antenna.

At the receiving end, RF signals are collected by the receiving antenna and at selected station . To obtain the picture transmitted. The output corresponding to the video signal is used to control the intensity of light in a cathode ray tube.An FM receiver is used to separate the audio signal and reproduce sound.

Q.46. Who given the first demonstration of TV in world?

Ans:- during 1927 by J.L. Baird (UK) and C.F. Jenkins(USA)The first demonstration of television, was given in world.

Q.47. In a transistor, which part is (a) highly doped (b) moderately doped (c) lightly doped?

Ans:-[a]Emitter is highly doped .
       -[b]Collector is moderately doped.
       -[c]Base is lightly doped.

Q.48. Why,Under ordinary conditions, semiconductors behave like insulators?

Ans:- Under ordinary conditions, electrons are not free and they involved in a covalent bond. Hence they behave like insulators.

Q.49 What is the reason for the rectifying action of a diode?

Ans:- In Forward bias of the diode,  low resistance causes the rectifying action of a diode