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Electronics Engineering
Electronics Engineering is a branch of engineering that deals with practical applications of electronic components, devices, systems, or equipment. Electronics are devices that operate on low voltage sources, as in electron tubes, transistors, integrated circuits, and printed circuit boards and use electricity as part of its driving force.
24,372 Questions
What is proportional integral controller?
This is related to control system and process control topic.
Proportional integral is the mode that result from a combination
of the proportional mode and the integral mode.
Why do you need test specifications in digital multimeters?
because it might output the wrong answer if not used in the right range/may be faulty/basically knowing its limitations
Do you have bsnl tta old question papers?
If the voltage applied across a capacitance is triangular in waveform then the waveform of the current is-
a) Triangular
b) Trapezoidal
c) Sinusoidal
d) Rectangular
Answer is :- Rectangular
1. One of the following statement which is true for relative dielectric constant is -
a) It is dimensionless
b) It is not equal to unity for vacuum
c) It?s value for all substances is less than one
d) None
Answer is :- It is dimensionless
2. Pure metals generally have-
a) high conductivity and low temperature coefficient
b) high conductivity and large temperature coefficient
c) low conductivity and zero temperature coefficient
d) low conductivity and high temperature coefficient
Answer is :- high conductivity and large temperature coefficient
3. For small size, high frequency coils, the most common core material is
a) Air
b) Ferrite
c) Powdered ion
d) Steel
Answer is :- Air
4. For an abrupt junction Varactor diode, the dependence of device capacitance (C) on applied reverse bias (V) is given by-
a) C a V1/3
b) C a V-1/3
c) C a V1/2
d) C a V-1/2
Answer is :- C a V-1/3
5. A superconductor is a-
a) A material showing perfect conductivity and Meissner effect below a critical temperature
b) A conductor having zero resistance
c) A perfect conductor with highest dimagnetic susceptibility
d) A perfect conductor which becomes resistive when the current density through it exceeds a critical value
Answer is :-A material showing perfect conductivity and Meissner effect below a critical temperature
6. When a semiconductor based temperature transducer has a temperature coefficient of ?2500 mV/0C then this transducer is indeed a-
a) Thermistor
b) Forward biased pn junction diode
c) Reverse biased pn junction diode
d) FET
Answer is :- Forward biased pn junction diode
7. The location of lightning arrestor is -
a) Near the transformer
b) Near the circuit breaker
c) Away from the transformer
d) None
Answer is :- Near the transformer
8. Time constant of an RC circuit increases if the value of the resistance is -
a) Increased
b) Decreased
c) Neither a nor b
d) Both a and b
Answer is :- Increased
9. Intrinsic semiconductors are those which -
a) Are available locally
b) Are made of the semiconductor material in its purest from
c) Have more electrons than holes
d) Have zero energy gaps
Answer is :- Are made of the semiconductor material in its purest from
10. The primary control on drain current in a JFET is exerted by -
a) Channel resistance
b) Size of depletion regions
c) Voltage drop across channel
d) Gate reverse bias
Answer is :- Gate reverse bias
11. The electrical conductivity of metals which is expressed in ohm-1 m-1 is of the order of -
a) 1010
b) 105
c) 10-4
d) 10-6
Answer is :- 105
12. When biased correctly, a zener diode ?
a) acts as a fixed resistance
b) has a constant voltage across it
c) has a constant current passing through it
d) never overheats
Answer is :- has a constant voltage across it
13. The current amplification factor adc is given by ?
a) IC/IE
b) IC/IB
c) IB/IC
d) IB/IC
Answer is :- IC/IE
14. Compared to bipolars, FETs have-
a) high input impedance
b) low input impedance
c) same input impedance
d) none
Answer is :- high input impedance
15. The source-drain channel of JFET is -
a) ohmic
b) bilateral
c) unilateral
d) both a and b
Answer is :- both a and b
16. diac is equivalent to a -
a) Pair of SCRs
b) Pair of four layer SCRs
c) Diode and two resistors
d) Triac width
Answer is :- Pair of four layer SCRs
17. When a sample of N type semiconductor has electron density of 6.25 ? 1011 /cm3 at 300K and if the intrinsic concentration of carriers in this sample is 2.5 ? 1013/cm3 then the hole density will be ?
a) 106/cm3
b) 103/ cm3
c) 1010/ cm3
d) 1012/ cm3
Answer is :- 103/ cm3
18. The statement ?In any network of linear impedances, the current flowing at any point is equal to the algebraic sum of the currents caused to flow at that point by each of the sources of emf taken separately with all other emf?s reduced to zero? represents -
a) Kirchhoff?s law
b) Norton?s theorem
c) Thevenin?s theorem
d) Superposition theorem
Answer is :- Superposition theorem
19. One of the following modes which has the characteristics of attenuation becoming less as the frequency is increased and is attractive at microwave frequencies of circular cylindrical wave guides is ?
a) TE1 mode
b) TM01 mode
c) TE01 mode
d) Higher order mode
Answer is :- TE01 mode
20. A two-port network is symmetrical if ?
a) z11z22 ? z12z21 = 1
b) h11h22 ? h12h21 = 1
c) AD ? BC = 1
d) y11y22 ? y12y21 = 1
Answer is :-AD ? BC = 1
21. For transmission line load matching over a range of frequencies, it is best to use a-
a) balun
b) broad band directional coupler
c) double stub
d) single stub of adjustable position
Answer is :- double stub
22. The poles and zeros of a driving point function of a network are simple and interlace on the negative real axis with a pole closest to the origin. It can be realised -
a) by an LC network
b) as an RC driving point impedance
c) as an RC driving point admittance
d) only by an RLC network
Answer is:- only by an RLC network
23. Poles and zeros of a driving point function of a network are simple and interlace on the jw axis. The network consists of elements ?
a) R and C
b) L and C
c) R and L
d) R, L and C
Answer is :- L and C
24. For a two port reciprocal network, the output open circuit voltage divided by the input current is equal to ?
a) B
b) Z12
c) ?
d) h12
Answer is :- Z12
25. In a short electric doublet the radiation properties are so that-
a) The induction field diminishes as the square root of the distance and is only appreciable in the vicinity of the conductor.
b) In the radiation, magnetic field is minimum when the current is maximum.
c) The radiation resistance of a short doublet antenna is extremely high.
d) Mean rate of power through a unit area of spherical sphere surrounding this doublet is proportional to the square of the elemental length, other factors remaining constant.
Answer is :-Mean rate of power through a unit area of spherical sphere surrounding this doublet is proportional to the square of the elemental length, other factors remaining constant.
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How was the cellphone originally made?
- In the 1930s the car radio phone was developed and put in service in several large cities. Even in cities that had dial phone exchanges all car radio phone calls were made through the operator and it was not uncommon to have to wait a half hour to connect to an operator to make a call. This system could not handle more than 3 to 12 total calls in one city, depending on the transmitter/receiver designs used.
- While working on solutions to the limit of 3 to 12 calls in one city, in 1947 Bell Labs researchers developed the concept of cellular communication, where an area would be divided into hexagonal cells and calls would be handed off from tower to tower as the car radio phone moved from one cell to another. However it was decided that the vacuum tube based electronics of the time could not meet the requirements of a cellular system, so A. T. & T. did not attempt to make cellular car radio phones.
- In 1969 A. T. & T. decided the semiconductor based electronics of the time could meet the requirements of a cellular system, so they began negotiations with the FCC for radio bandwidth allocation and began the design of cellular car radio phones (they had no plans to attempt designing handheld cellphones).
- In 1971 Motorola designed the first handheld cellphone. However mostly due to limitations of the rechargeable batteries of the time, this cellphone was about the size and weight of a brick and the batteries ran down in about an hour. It proved that handheld cellphones were possible, but itself was not really practical for use by the public.
- In the 1980s and 1990s improvements in miniaturization of electronics and batteries with more capacity gradually made the handheld cellphone truly practical. By the end of the 1980s the now obsolete original car radio phone systems were all shutdown and replaced with cell towers, although car cellphones remained in use for a while where calls still had to be made through an operator (safer than dialing while driving).
Why do you use logarithm to calculate gain of amplifiers?
Audio engineers talk about the "JND", which stands for "just notiecable difference", which is a 3 decibel gain. That 3 decibel gain requires a doubling of amplifier power. For an amp to sound, subjectively, "twice as loud" requires a tenfold increase in power (300 watts instead of 30 watts).
The decibel scale is logarithmic, not arithmetic.
30 ohms
AnswerAn incandescent lamp doesn't obey Ohm's Law, because the ratio of voltage to current changes as the supply voltage is varied. All you can say is that, when the applied voltage is 9.0 V, then the resistance will happen to be 30 ohms. If you change the applied voltage to some other value, then you will find the resistance will have changed too.Ohm's Law isn't a universal law; in fact, most materials and circuit devices do not obey Ohm's Law, and tungsten, from which lamp filaments are manufactured, is an example of a metal that does not obey Ohm's Law (we call them 'non-linear' or 'non-ohmic')
Definition of fundamental and derived units?
- Time
- Space (or length)
- Mass
- Temperature
- Electrical current
- Luminosity
- Amount of matter
A fundamental quantity is an irreducible "thing". It cannot be described in terms of other "things". This is in contrast to derived quantities, which can be described in terms of other "things". Fundamental quantities are also called base quantities
Fundamental quantities can be considered to be dimensions, but in a loose context. In physics, when we refer to dimensions, we usually refer to space and time (and theoretically higher similar dimensions), and not the dimension of the luminosity (see below).
Each fundamental quantity has an associated unit in the SI system:
- Time: seconds (s)
- Space: meters (m)
- Mass: kilograms (kg)
- Temperature: degrees kelvin (K)
- Electrical current: ampere (A)
- Luminosity: candela (l)
- Amount of matter: mole
There are no such things as SI 'derived units'; the correct term is 'base units'.
How a photocell generates electricity?
When the p and n are joined together they form what is called the "p-n junction." When they are joined some of the electrons from the n side of the junction move to the p side. When certain kinds of light hit the photovoltaic cell, some of the electrons move from the p side to the n side. In both cases the electrons have gained energy and can pass through a circuit--this creates an electrical current.
What materials conducts heat well?
Metals (periodic table metals) and some Metalliods (also called semi-conductors) under certain conditions.
How do you analyze the internal circuit of LM386?
One of the beauties of an integrated circuit is that you can regard the package as
a 'black box' characterized by its published operating parameters, and you don't
need to analyze the internal circuit.
If you've been assigned to analyze the internal circuit, then you're part of a class
or group of people who have been given the tools necessary to do it. Just go
ahead and dig into the nine transistors there in the LM386. There's a single-stage
differential amplifier with a few feedback components, and there's also what appears
to be a voltage regulator. There's not really that much in there, and you shouldn't be
scared off by the use of PNP and NPN transistors in cascade.
The whole thing is just an academic exercise anyway ... notice that the drawing
in the data sheet is labeled "equivalent schematic", and doesn't really represent
everything that's actually on the chip.
Digital sound is a rather silly name.
Digital refers to how the sound is stored, as a huge number of ones and zeros. Ths stream of ones and zeros can then be fed as instructions to something like a computer, or something that works like a computer, and the computer will understand the instructions and turn them into something called an analouge(or analog)electric signal which then can be turned into sound by a set of headphones or speakers.
Sound, the "thing" that we hear, is never digital.
Yes, some of them do. Most common remote controls for home entertainment systems include an infrared (IR) light emitting diode (LED) that uses the IR to communicate from the remote control to the equipment. Your equipment can "see" the light from the remote control, but if you look into the "business end" of the device and actuate it, you can't see anything. Simple and easy.
Why do you care about polarity in AC circuits?
There are two reasons one cares about polarity in AC circuits: safety and phasing.
In a common household circuit, we are concerned with safety. One side of the AC line, called the "neutral", is at the same voltage as ground. This side of a common outlet is identified by the wider slot and plugs have a wider blade. In the wiring, the neutral is white. On wiring devices, the neutral wire connects to a silver colored screw. On appliance cords, especially flat, two-wire "zip" cord, the neutral side usually has a rib or ribs to identify it. Sometimes this rib is very subtle, like a square corner on the neutral lead where the hot lead is completely round.
The other side of the line is the "line" or "hot" wire. In household wiring, this side is black or red. It corresponds to the narrow slot in an outlet and connects to a brass colored screw.
Circuit breakers and switches are supposed to be wired in the hot lead so if they are turned off, both sides of the connected receptacle or light socket are at neutral potential. If this were not the case, you could get a shock from a light socket which is turned off, if you were also touching a grounded contact of some kind. For further safety, the larger annular threaded contact in a light socket is supposed to be connected to the neutral and the smaller button contact to the line side.
Years ago, this was even more important because household electrical appliances were often made of metal. Plastic wasn't as common. The metal would sometimes be connected to the neutral wire. If the polarity was reversed, the metal case would be "hot". Many old tube-type radios had no transformer in their power supply and the chassis was connected directly to the wide blade of the plug. If the receptacle was wired wrong, the whole radio would be "hot".
The second reason we care, phase, relates to more complex wiring such as three-phase circuits and in electronics. AC voltages are really DC voltages at any particular instant in time and thus have polarity. The polarity of these instantaneous DC voltages is just as important, and for the same reasons, as constant DC voltages.
"Phase" refers to the relative polarity of these instantaneous DC voltages among a related group of AC voltages. If you wire two AC sources in series and they are "in phase" then the voltages add as expected. If one source is reversed, then the voltages subtract. Similarly, paralleling two AC sources which are out of phase, will have the same result as paralleling two DC sources with opposite polarity - a fire.
What color represent for clockwise in potentiometer?
There is no color code for potentiometers as it is variable.
Why very low frequency is having no use for data transfer in computer network?
Low frequency devices are losing popularity in computer networking because of their slow transfer rates. The higher the frequency of a device the faster it can transfer data.
What is importance of band gap in semiconductors?
bandgap has an importance role for conduction.if bandgap is max,the conduction of electron is min. and vice-versa.hence we can say that the bandgap desides the conductivity of any material(may be metal or nonmetal)
What did integrated circuits replaced?
The integrated circuit replaced vacuum tubes in electronic devices. This improved electronic devices because the two main problems with vacuum tubes were: 1. Heat generation/ power consumption and 2. Fragility
What effect does decreased resistance have on a circuit?
resistance is the opposition to the flow of an electric current, therefore the current will decrease as the resistance increases. Resistance also creates heat. This is how the light globes in a circuit light up.
What is the acceptable range of ac voltage at an outlet?
The acceptable range of ac voltage at an outlet is from 115 to 120 volts. The utility company has a mandate to keep the voltage within a 10% fluctuation range. The catch is 10% from what set point voltage.
Differences between Intel 8051 and atmel 89c51 micro controller?
The instructions used by Atmel 89CXX and 89CXXXX are the same or subset of 8051 microcontrollers.
- Fully static operation,
- flash program memory,
- less pin count and
- precision analog comparator ( in case of 89C20510)
are some of the attractions in going for these microcontrollers. Due to many similar features in the architecture and instruction and instruction set as that of 8051, it becomes possible for the 8051 designer to directly start using 89CXX and 89C20XX microcontrollers without any more efforts in learning these microcontrollers.
Why In Clippers And Clampers 0.6 Volt Is Reduced?
.6v is the peak inverse voltage drop of a silicon made diode.
ANSWER: A diode will have a .6 to .7 volts drop [depending on current] in the FORWARD conduction mode. In the inverse it could be 50 to 1000 volts depends on the diode.
