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Electrical Engineering
Electrical engineering is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism.
23,056 Questions
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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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
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'.
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')
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.
What happen when single phase supply of induction motor interrupted while driving the load?
That happens when the supply is turned off, and the motor runs down and stops.
That's an 11% overvoltage (460/415), so this may be reaching the design limits of the transformer. If the system is actually run hot (say 105% of 460, or 480v), then I'd say no, unless specifically stated in test reports or design criteria. You should ask the manufacturer to be sure.
What is cascade tripping and how it happens?
cascade tripping or failure is a failure in a system of interconnected parts in which the failure of part can trigger the failure of successive part.it means that failure in one part of system may quickly spread into entire system .
cascade tripping occurs for several reason
-when component of grid is over stressed
-generator shut down due to any reason
-if transmission line has too much current following on it, and it will heat up and conductor fails
-when tree are close to transmission line ,electric current from line will produce arc ,and circuit breaker disconnect line .
-natural climate like earthquake ,heavy rain etc ,in which pole are fall down.
Vidio how to function phase inverter?
http://wiki.answers.com/Q/Vidio_how_to_function_phase_inverter"
How does the electric engine of the Toyota 'Hybird' Prius work?
It works great! At speeds under 30 MPH the gasoline engine does not run until the main battery needs a charge. Battery is also charged by regeneration from the wheels.
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.
In a 220 volt AC single phase circuit the voltage from either leg to the neutral is?
The proper terminology is L1,L2,N. N is for neutral and it is this wire that is grounded. The voltage measurement from the L1 to N will give you 120 volts. Also from L2 to N will give you 120 volts and as you know from L1 to L2 will give you 240 volts. Single pole breakers in the panel board starting at the top, alternate between L1 and L2 all the way down to the bottom. These breakers all have 120 volt outputs. If you plug a 2 pole breaker into two slots then you get 240 outputs because L1 and L2 are adjacent to one another.
Will lights in a series circuit will stay lit if one goes out?
Like the old Christmas tree lights, no; lights connected in series will not stay lit if one (or more) are either burned out or disconnected from the circuit. Lights in series are connected "head-to-tail". Take one out, and the circuit is incomplete and will not work.
Would a defective governor cause a generator motor not run?
Yes, if the governor failed in a way that "makes it think" the generator is always running too fast it might prevent the generator from running at all.
What cause current on the neutral line in a three phase?
Current on neutral in a multi phase system is caused by imbalance between the phases.
Question: Are you talking about neutral or ground? The two are very different. Although neutral is grounded, it is expected to be a current carrying conductor, so current on neutral is normal, so to speak. Ground, on the other hand is a protective circuit that is not supposed to have any current on it at all.
How To Sell Your Used Diesel Generator?
Diesel generators are well known for their reliability. Where gas and propane add friction to the various moving parts inside a machine, diesel lubricates them, meaning less wear and tear and most important, less repair. However, sometimes a person no longer needs their ever reliable diesel generator so they decide to sell it. This article will tell you how to sell your used diesel generator to generate some extra income.
First, compile as much information about your generator as possible. Buyers will want to know how many cylinders it runs on, what size the fuel tank is, how it’s cooled, its fuel consumption, noise level, maximum output, weight and voltage.
Second, take pictures of your generator. A full picture along with shots of its ID tags, hour meter and engine will help.
The next step is to decide how you want to sell it. You can sell it through print or online. For print, you can put adds in your local newspaper and trade magazines for a small fee. For selling it online, www.ebay.com, www.craigslist.com and www.equipmatching.com are the three most popular sites. Ebay is the largest online auction house and might draw the biggest pool of potential buyers, but they do charge a commission for each sale, where Craigslist and EquipMatching do not. Craigslist is probably the easiest, considering you don’t even have to create an account in order to sell there and signing up is free. EquipMatching, however, is also free as well as being dedicated entirely to surplus machinery. They also offer paid memberships that will improve your chances of getting your item noticed and sold. All these sources publish want ads, so be sure to check them first because you might end up saving yourself a little extra work.
Www.dieselserviceandsupply.com is another great option. Diesel Service & Supply, Inc. specializes in diesel generators with outputs between 50kw and 3mw and has been buying and selling diesel generators for more than 20 years. To find out if they’re interested in your generator, simply fill out the form on their website and email them your pictures.
What is the biggest size of single phase transformer?
Today the highest voltages are 800 kV. These are commercially installed transformers that are used for the transmission of power throughout the grid that they are connected to.
What can you measure with amperes?
Current is measured in amperes. Amperes is also coulombs per second.
How do you calculate power if flowpressure and efficiency is given?
formula are given at www.calculatoredge.com
How do you understand the leak in vacuum bottle of vacuum circuit breaker without high voltage test?
Understanding the components of the vacuum bottle, one can be in better position of understanding the leakage. Microprocessor monitors leakage in the Vacuum bottle.
What is the working principle of AC servo motor?
A servomotor is used within a position-control or speed-control feedback control system. Servomotors are used in applications such as machine tools, pen plotters, and other control systems.
An electrostatic motor is based on the attraction and repulsion of electric charge
A Torquemotor (also known as a limited torque motor) is a specialized form of Induction_motorwhich is capable of operating indefinitely while Stall_(engine), that is, with the Rotor_(electric) blocked from turning, without incurring damage
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