BSNL MT TELECOM OPERATIONS 1. Materials and Components 2. Physical Electronics, Electron Devices and ICs 3. Signals and Systems 4. Network theory 5. Electromagnetic Theory 6.Electronic Measurements and Instrumentation 7. Analog Electronic Circuits 8. Digital Electronic Circuits 9. Control Systems 10. Communication Systems 11. Microwave Engineering 12. Computer Engineering 13. Power Electronics
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BSNL MT
TELECOM OPERATIONS
1. Materials and Components
2. Physical Electronics, Electron Devices and ICs
3. Signals and Systems
4. Network theory
5. Electromagnetic Theory
6.Electronic Measurements and Instrumentation
7. Analog Electronic Circuits
8. Digital Electronic Circuits
9. Control Systems
10. Communication Systems
11. Microwave Engineering
12. Computer Engineering
13. Power Electronics
1.The S.I. unit of power is (a) henry (b) coulomb (c) watt (d) watt-hour Ans: c 2. Electric pressure is also called (a) resistance (b) power (c) voltage (d) energy Ans: c 3.The substances which have a large number of free electrons and offer a low resistance are called (a) insulators (b) inductors (c)semi-conductors (d)conductors Ans: d 4.Out of the following which is not a poor conductor ? (a) Cast iron (b) Copper (c) Carbon (d) Tungsten Ans: b 5.Out of the following which is an insulating material ? (a) Copper (b) Gold (c) Silver (d) Paper Ans: d 1. Laminations of core are generally made of (a) case iron (b) carbon (c)silicon steel (d)stainless steel Ans: c 2. Which of the following could be lamina-proximately the thickness of lamina-tions of a D.C. machine ? (a)0.005 mm (b)0.05 mm (c)0.5 m (d)5 m Ans: c 3. The armature of D.C. generator is laminated to (a) reduce the bulk (b) provide the bulk (c)insulate the core (d)reduce eddy current loss Ans: d 4.The resistance of armature winding depends on (a) length of conductor (b) cross-sectional area of the conductor (c)number of conductors (d)all of the above Ans: d 5.The field coils of D.C. generator are usually made of (a) mica (b) copper (c) cast iron (d) carbon Ans: b
1.The property of coil by which a counter e.m.f. is induced in it when the current through the coil changes is known as (a) self-inductance (b) mutual inductance (c) series aiding inductance (d) capacitance Ans: a 2.As per Faraday's laws of electromagnetic induction, an e.m.f. is induced in a conductor whenever it (a) lies perpendicular to the magnetic flux (b) lies in a magnetic field (e) cuts magnetic flux (d) moves parallel to the direction of the magnetic field Ans: c 3.Which of the following circuit element stores energy in the electromagnetic field ? (a) Inductance (b) Condenser (c) Variable resistor (d) Resistance Ans: a 4.The inductance of a coil will increase under all the following conditions except (a) when more length for the same number of turns is provided (6) when the number of turns of the coil increase (c) when more area for each turn is provided (d) when permeability of the core increases Ans: a 5. Higher the self-inductance of a coil, (a) lesser its weber-turns (b) lower the e.m.f. induced (c) greater the flux produced by it (d) longer the delay in establishing steady current through it Ans: d 1.A sine wave has a frequency of 50 Hz. Its angular frequency is _______ radian/second. (a) 100 n (b) 50 jt (c) 25 jt (d) 5 n Ans: a 2.The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20 Q. If frequency is increased to 100 Hz, reactance becomes_____ohms. (a) 2.5 (b) 5 (c) 10 (d) 15 Ans: c 3.The period of a wave is (a) the same as frequency (b) time required to complete one cycle (c)expressed in amperes (d)none of the above Ans: b
4.The form factor is the ratio of (a) peak value to r.m.s. value (b) r.m.s. value to average value (c)average value to r.m.s. value (d)none of the above Ans: b 5.The period of a sine wave is _____ seconds. Its frequency is (a) 20 Hz (b) 30 Hz (c) 40 Hz (d) 50 Hz Ans: d 1. The insulating material for a cable should have (a) low cost (b) high dielectric strength (c) high mechanical strength (d) all of the above Ans: d 2. Which of the following protects a cable against mechanical injury ? (a) Bedding (b) Sheath (c) Armouring (d) None of the above Ans: c 3. Which of the following insulation is used in cables ? (a) Varnished cambric (b) Rubber (c) Paper (d) Any of the above Ans: d 4. Empire tape is (a) varnished cambric (b) vulcanised rubber (c) impregnated paper (d) none of the above Ans: a 5. The thickness of the layer of insulation on the conductor, in cables, depends upon (a) reactive power (b) power factor (c) voltage (d) current carrying capacity Ans: c 1. In an open loop control system (a) Output is independent of control input (b) Output is dependent on control input (c) Only system parameters have effect on the control output (d) None of the above Ans: a
2. For open control system which of the following statements is incorrect ? (a) Less expensive (b) Recalibration is not required for maintaining the required quality of the output (c) Construction is simple and maintenance easy (d) Errors are caused by disturbances Ans: b 3. A control system in which the control action is somehw dependent on the output is known as (a) Closed loop system (b)Semiclosed loop system (c)Open system (d)None of the above Ans: a 4. In closed loop control system, with positive value of feedback gain the overall gain of the system will (a) decrease (b) increase (c) be unaffected (d) any of the above Ans: a 5. Which of the following is an open loop control system ? (a) Field controlled D.C. motor (b) Ward leonard control (c)Metadyne (d)Stroboscope Ans: a 1.The property of coil by which a counter e.m.f. is induced in it when the current through the coil changes is known as (a) self-inductance (b) mutual inductance (c) series aiding inductance (d) capacitance Ans: a 2.As per Faraday's laws of electromagnetic induction, an e.m.f. is induced in a conductor whenever it (a) lies perpendicular to the magnetic flux (b) lies in a magnetic field (e) cuts magnetic flux (d) moves parallel to the direction of the magnetic field Ans: c 3.Which of the following circuit element stores energy in the electromagnetic field ? (a) Inductance (b) Condenser (c) Variable resistor (d) Resistance Ans: a 4.The inductance of a coil will increase under all the following conditions except (a) when more length for the same number of turns is provided (6) when the number of turns of the coil increase (c) when more area for each turn is provided (d) when permeability of the core increases Ans: a 5. Higher the self-inductance of a coil, (a) lesser its weber-turns (b) lower the e.m.f. induced (c) greater the flux produced by it (d) longer the delay in establishing steady current.
Ans: d 1. The converse of hardness is known as (a) malleability (b) toughness (c) softness (d) none of the above Ans: c 2. On which of the following factors does the resistivity of a material depend ? (a)Resistance of the conductor (b)Area of the conductor section (c)Length of the conductor (d) All of the above Ans: d 3. Is a negatively charged particle present in an atom. (a) Proton (b)Neutron (c)Electron (d) None of the above Ans: c 4. The formula ____ determines the number of electrons that can be accommodated in any level. (a) 2n2 (b)4n2 (c)2n3 (d)4ns Ans: a 5. The tiny block formed by the arrangement of a small group of atoms is called the (a) unit cell (b)space lattice (c)either (a) or (b) (d) none of the above Ans: a 1."The mass of an ion liberated at an electrode is directly proportional to the quantity of electricity". The above statement is associated with (a)Newton's law (b)Faraday's law of electromagnetic (c)Faraday's law of electrolysis (d)Gauss's law Ans: c 2.The charge required to liberate one gram equivalent of any substance is known as ______ constant (a) Time b) Faraday's (c) Boltzman Ans: b 3.During the charging of a lead-acid cell (a) its voltage increases (b) it gives out energy (c) its cathode becomes dark chocolate brown in colour (d) specific gravity of H2SO4 decreases Ans: a
4.The capacity of a lead-acid cell does not depend on its (a) temperature (b) rate of charge (c) rate of discharge (d) quantity of active material Ans: b 5.During charging the specific gravity of the electrolyte of a lead-acid battery (a) increases (b) decreases (c) remains the same (d) becomes zero Ans: a 1. The force between two charges is 120 N. If the distance between the charges is doubled, the force will be (a) 60 N (b) 30 N (c) 40 N (d) 15 N Ans: b 2. The electric field intensity at a point situated 4 metres from a point charge is 200 N/C. If the distance is reduced to 2 metres, the field intensity will be (a) 400 N/C (b) 600 N/C (c) 800 N/C (d) 1200 N/C Ans: c 3. The lines of force due to charged particles are (a) always straight (b) always curved (c) sometimes curved (d) none of the above Ans: b 4. The electric field at a point situated at a distance d from straight charged conductor is (a) proportional to d (b) inversely proportional to d (c) inversely proportional to d (d) none of the above Ans: b 5. The direction of electric field due +0 positive charge is . (a) away from the charge (b) towards the charge (c) both (a) and (6) (d) none of the above Ans: a
6. A field line and an equipotential surface are (a) always parallel (b) always at 90° (c) inclined at any angle 0 (d) none of the above Ans: b 7. The ability of charged bodies to exert force on 6ne another is attributed to the existence
of
(a) electrons
(b) protons
(c) neutrons
(d) electric field
Ans: d
8. If the sheet of a bakelite is inserted between the plates of an air capacitor, the capacitance
will
(a) decrease
(b) increase
(c) remains unchanged
(d) become zero
Ans: b
9. A capacitor stores 0.24 coulombs at 10 volts. Its capacitance is
(a) 0.024 F
(b) 0.12 F
(c) 0.6 F
(d) 0.8 F
Ans: a
10. For making a capacitor, it is better to select a dielectric having
(a) low permittivity
(b) high permittivity
(c) permittivity same as that of air
(d) permittivity slightly more than that of air
Ans: b
11. The units of capacitance are
(a) volts/coulomb
(b) coulombs/volt
(c) ohms
(d) henry/Wb
Ans: b
12. If three 15 uF capacitors are connected in series, the net capacitance is
(a) 5 uF
(6) 30 uF
(c) 45 uF
(d) 50 uF
Ans: a
13. If three 10 uF capacitors are connected in parallel, the net cararitanceis
(a) 20 uF
(b) 30 uE
(c) 40 uF
(d) 50 uF
Ans: b
14. A dielectric material must be
(a) resistor
(b) insulator
(c) good conductor
(d) semi conductor
Ans: b
15. An electrolytic capacitor can be used for
(a) D.C. only
(b) AC. only
(c) both D.C. as well as A.C.
Ans: a
16. The capacitance of a capacitor is not affected by
(a) distance between plates
(6) area of plates
(c) thickness of plates
(d) all of the above
Ans: c
17. Which of the following is not a vector ?
(a) Linear momentum
(b) Angular momentum
(c) Electric field
(d) Electric potential
Ans: b
18. Two plates of a parallel plate capacitor after being charged from a constant voltage source
are separated apart by means of insulated handles, then the
(a) Voltage across the plates increases
(b) voltage across the plates decreases
(c) charge on the capacitor decreases
(d) charge on the capacitor increases
Ans: b
19. If A.C. voltage is applied to capacitive circuit, the alternating current can flow in the circuit
because
(a) varying voltage produces the charg¬ing and dicharging currents
(b) of high peak value
(c) charging current can flow
(d) discharge current can flow
Ans: a
20. Voltage applied across a ceramic dielectric produces an electrolytic field 100 times greater
than air. What will be the value of dielectric constant ?
(a) 50
(6) 100
(c) 150
(d) 200
Ans: b
21. Which of the following statements is correct ?
(a) Air capacitors have a blackband to indicate the outside foil
(6) Electrolytic capacitor must be con¬nected in the correct polarity
(c) Ceramic capacitors must be con¬nected in the correct polarity
(d) Mica capacitors are available in capacitance value of 1 to 10 pF
Ans: b
22. The dissipation factor of a good dielectric is of the order of
(a) 0.0002
(b) 0.002
(c) 0.02
(d) 0.2
Ans: a
23. "The total electric flux through any closed surface surrounding charges is equal to the
amount oflcharge enclosed".
The above statement is associated with
(a) Coulomb's square law
(b) Gauss's law
(c) Maxwell's first law
(d) Maxwell's second law
Ans: b
24. Three capacitors each of the capacity C are given. The resultant capacity 2/3 C
can be obtained by using them
(a) all in series
(b) all in parallel
(c) two in parallel and third in series with this combination
(d) two in series and third in parallel across this combination
Ans: c
25. For which of the following parameter variation, the capacitance of the capacitor remains
unaffected ?
(a) Distance between plates
(b) Area of the plates
(c) Nature of dielectric
(d) Thickness of the plates
Ans: d
26. Which of the following statement is true ?
(a) The current in the discharging capacitor grows linearly
(b) The current in the dicharging capacitor grows exponentially
(c) The current in the discharging capacitor decays exponentially
(d) The current in the discharging capacitor decreases constantly
Ans: b
27. Which of the following expression is correct for electric field strength ?
(a) E = D/E
(b) E = D2/t
(c) E = jtD
(d) E= nD2
Ans: a
28. In a capacitor the electric charge is stored in
(a) metal plates
(b) dielectric
(c) both (a) and (6)
(d) none of the above
Ans: b
29. Which of the following materials has the highest value of dielectric constant?
(a) Glass
(b) Vacuum
(c) Ceramics
(d) Oil
Ans: c
30. Which of the following capacitors will have the least variation ?
(a) Paper capacitor
(b) Ceramic capacitor
(c) Silver plated mica capacitor
(d) None of the above
Ans: c
1. Which of the following is an advantage of heating by electricity ? (a) Quicker operation (b) Higher efficiency (c) Absence of flue gases (d) All of the above Ans: d 2. ________ has the highest value of thermal conductivity.
(a) Copper (b) Aluminium (c) Brass (d) Steel Ans: a 3. Which of the following heating methods has maximum power factor ? (a) Arc heating (b) Dielectric heating (c) Induction heating (d) Resistance heating Ans: d 4 method has leading power factor (a) Resistance heating (b) Dielectric heating (c) Arc heating (d) Induction heating Ans: b 5 is used for heating non-conducting materials. (a) Eddy current heating (b) Arc heating (c) Induction heating (d) Dielectric heating Ans: d
1. An air gap is usually inserted in magnetic circuits to (a) increase m.m.f. (b) increase the flux (c) prevent saturation (d) none of the above Ans: c 2. The relative permeability of a ferromagnetic material is (a) less than one (b) more than one (c) more than 10 (d) more than 100 or 1000 Ans: d 3. The unit of magnetic flux is (a) henry (b) weber (c) ampereturn/weber (d) ampere/metre Ans: b 4. Permeability in a magnetic circuit corresponds to______ in an electric circuit. (a) resistance (b) resistivity (c) conductivity (d) conductance Ans: c 5. Point out the wrong statement. Magnetic leakage is undesirable in electric machines because it (a) lowers their power efficiency (b) increases their cost of manufacture (c) leads to their increased weight (d) produces fringing Ans: a 1. Kirchhoff s current law states that (a) net current flow at the junction is positive (b) Hebraic sum of the currents meeting at the junction is zero (c) no curreht can leave the junction without some current entering it. (d) total sum of currents meeting at the junction is zero Ans: b 2. According to Kirchhoffs voltage law, the algebraic sum of all IR drops and e.m.fs. in any closed loop of a network is always (a) negative
(b) positive (c) determined by battery e.m.fs. (d) zero Ans: d 3. Kirchhoffs current law is applicable to only (a) junction in a network (b) closed loops in a network (c) electric circuits (d) electronic circuits Ans: a 4. Kirchhoffs voltage law is related to (a) junction currents (b) battery e.m.fs. (c) IR drops (d) both (b) and (c) (e) none of the above Ans: d 5. Superposition theorem can be applied only to circuits having (a) resistive elements (b) passive elements (c) non-linear elements (d) linear bilateral elements Ans: d 1.Which of the following component is usually fabricated out of silicon steel ? (a) Bearings (b) Shaft (c) Statorcore (d) None of the above Ans: c 2. The frame of an induction motor is usually made of (a) silicon steel (b) cast iron (c) aluminium (d) bronze Ans: b 3. The shaft of an induction motor is made of (a) stiff (b) flexible (c) hollow (d) any of the above Ans: a
4. The shaft of an induction motor is made of (a) high speed steel (b) stainless steel (c) carbon steel (d) cast iron Ans: c 5. In an induction motor, no-load the slip is generally (a) less than 1% (b) 1.5% (c) 2% (d) 4% Ans: a 1. By which of the following systems electric power may be transmitted ? (a) Overhead system (b) Underground system (c) Both (a) and (b) (d) None of the above Ans: c 2 are the conductors, which connect the consumer's terminals to the distribution (a) Distributors (b) Service mains (c) Feeders (d) None of the above Ans: b 3. The underground system cannot be operated above (a) 440 V (b) 11 kV (c) 33 kV (d) 66 kV Ans: d 4. Overhead system can be designed for operation upto (a) 11 kV (b) 33 kV (c) 66 kV (d) 400 kV Ans: c 5. If variable part of annual cost on account of interest and depreciation on the capital outlay is equal to the annual cost of electrical energy wasted in the conductors, the total annual cost will be minimum and the corresponding size of conductor will be most economical. This statement is known as (a) Kelvin's law (b) Ohm's law (c) Kirchhoffs law (d) Faraday's law (e) none of the above Ans: a
1) Resistivity of a wire depends on A. material B. length C. cross section area D. all of above 2) When n numbers resistances of each value r are connected in parallel, then the resultant resistance is x. When these n resistances are connected in series, total resistance is A. nx. B. n2x. C. x/n. D. rnx. 3) Resistance of a wire is r ohms. The wire is stretched to double its length, then its resistance will be A. r/2 B. 4r C. 2r D. r/4 4) Kirchhoff’s second law is based on law of conservation of A. charge B. energy C. momentum D. Mass 5) One coulomb of electrical charge is contributed by how many electrons ? A. 0.625 X 1019. B. 1.6 X 1019. C. 1019. D. 1.6 X 1012. 1.The number of digits in octal system is a.8 b.7 c.10 d. none 2..The number of digits in Hexadecimal system is a.15 b.17 c.16 d. 8 3.The number of bits in a nibble is a.16 b.5 c.4 d.8 4.The digit F in Hexadecimal system is equivalent to —— in decimal system a.16 b.15 c.17 d. 8 5.Which of the following binary numbers is equivalent to decimal 10 a.1000 b.1100 c.1010 d.1001 1. In an open loop control system (a) Output is independent of control input (b) Output is dependent on control input (c) Only system parameters have effect on the control output (d) None of the above Ans: a 2. For open control system which of the following statements is incorrect ? (a) Less expensive (b) Recalibration is not required for maintaining the required quality of the output
(c) Construction is simple and maintenance easy (d) Errors are caused by disturbances Ans: b 3. A control system in which the control action is somehw dependent on the output is known as (a) Closed loop system (b)Semiclosed loop system (c)Open system (d)None of the above Ans: a 4. In closed loop control system, with positive value of feedback gain the overall gain of the system will (a) decrease (b) increase (c) be unaffected (d) any of the above Ans: a 5. Which of the following is an open loop control system ? (a) Field controlled D.C. motor (b) Ward leonard control (c)Metadyne (d)Stroboscope Ans: a 1. The force between two charges is 120 N. If the distance between the charges is doubled, the force will be (a) 60 N (b) 30 N (c) 40 N (d) 15 N Ans: b 2. The electric field intensity at a point situated 4 metres from a point charge is 200 N/C. If the distance is reduced to 2 metres, the field intensity will be (a) 400 N/C (b) 600 N/C (c) 800 N/C (d) 1200 N/C Ans: c 3. The lines of force due to charged particles are (a) always straight (b) always curved (c) sometimes curved (d) none of the above Ans: b 4. The electric field at a point situated at a distance d from straight charged conductor is (a) proportional to d (b) inversely proportional to d (c) inversely proportional to d (d) none of the above
Ans: b 5. The direction of electric field due +0 positive charge is . (a) away from the charge (b) towards the charge (c) both (a) and (6) (d) none of the above Ans: a 1.A sine wave has a frequency of 50 Hz. Its angular frequency is _______ radian/second. (a) 100 n (b) 50 jt (c) 25 jt (d) 5 n Ans: a 2.The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20 Q. If frequency is increased to 100 Hz, reactance becomes_____ohms. (a) 2.5 (b) 5 (c) 10 (d) 15 Ans: c 3.The period of a wave is (a) the same as frequency (b) time required to complete one cycle (c)expressed in amperes (d)none of the above Ans: b 4.The form factor is the ratio of (a) peak value to r.m.s. value (b) r.m.s. value to average value (c)average value to r.m.s. value (d)none of the above Ans: b 5.The period of a sine wave is _____ seconds. Its frequency is (a) 20 Hz (b) 30 Hz (c) 40 Hz (d) 50 Hz Ans: d 6.A heater is rated as 230 V, 10 kW, A.C. The value 230 V refers to
(a) average voltage (b) r.m.s. voltage
(c) peak voltage (d) none of the above
Ans: b
7.If two sinusoids of the same frequency but of different amplitudes and phase angles are
subtracted, the resultant is
(a) a sinusoid of the same frequency (b) a sinusoid of half the original frequency
(c) a sinusoid of double the frequency (d) not a sinusoid
Ans: a
8. The peak value of a sine wave is 200 V. Its average value is
(a) 127.4 V (b) 141.4 V
(c) 282.8 V (d)200V ANS: A
9.If two sine waves of the same frequency have a phase difference of JT radians, then
(a)both will reach their minimum values at the same instant
(b)both will reach their maximum values at the same instant
(c)when one wave reaches its maximum value, the other will reach its minimum value
(d)none of the above
Ans: c
10.The voltage of domestic supply is 220V. This figure represents
(a) mean value (b) r.m.s. value
(c) peak value (d) average value
Ans: a
11.Two waves of the same frequency have opposite phase when the phase angle between them is
(a) 360° (b) 180°
(c) 90° (d) 0°
Ans: b
12.The power consumed in a circuit element will be least when the phase difference between the
current and voltage is
(a) 180" (b) 90°
(c) 60° (d) 0°
Ans: b
13.The r.m.s. value and mean value is the same in the case of
(a) triangular wave (b) sine wave
(c) square wave (d) half wave rectified sine wave
Ans: c
14.For the same peak value which of the following wave will 'have the highest r.m.s. value ?
(a)square wave (b)half wave rectified sine wave
(c)triangular wave (d)sine wave
Ans: a
15.For the same peak value, which of the following wave has the least mean value ?
(a) half wave rectified sine wave (b) triangular wave
(c) sine wave (d) square wave
Ans: a
16.For a sine wave with peak value Imax the r.m.s. value is
(a) 0.5 Imax (b) 0.707 (c) 0.9 (d) 1.414 Lmax
Ans: b
17.Form Factor is the ratio of
(a) average value/r.m.s. value (b) average value/peak value
(e) r.m.s. value/average value (d) r.m.s. value/peak value
Ans: c
18.Form factor for a sine wave is
(a) 1.414 (b) 0.707 (c) 1.11 (d) 0.637
Ans: c
19.For a sine wave with peak value Emax______8.30. the average value is
20.For a frequency of 200 Hz, the time period will be
(a) 0.05 s (b) 0.005 s (c) 0.0005 s (d) 0.5 s
Ans: b
21.The phase difference between voltage and current wave through a circuit element is given as
30°. The essential condition is that
(a) both waves must have same frequency
(b) both waves must have identical peak values
(c) both waves must have zero value at the same time
(d) none of the above
Ans: a
22.The r.m.s. value of a sinusoidal A.C. current is equal to its value at an angle of______degrees.
(a) 90 (b) 60 (c) 45 (d) 30
Ans: c
23.Capacitive reactance is more when
(a) capacitance is less and frequency of supply is less
(b) capacitance is less and frequency of supply is more
(c)capacitance is more and frequency of supply is less
(d)capacitance is more and frequency of supply is more
Ans: a
24.In a series resonant circuit, the impedance of the circuit is
(a) minimum (b) maximum (c) zero (d) none of the above
Ans: a
25.Power factor of an electrical circuit is equal to
(a)R/Z (b)cosine of phase angle difference between current and voltage
(c)kW/kVA (d)ratio of useful current to total current Iw/I (e)all above Ans : e
26.The best place to install a capacitor is
(a)very near to inductive load (b)across the terminals of the inductive load
(c)far away from the inductive load (d)any where
Ans: b
27.Poor power factor
(a) reduces load handling capability of electrical system
(b) results in more power losses in the electrical system
(c) overloads alternators, transformers and distribution lines
(d) results in more voltage drop in the line
(e) results in all above
Ans: e
28.Capacitors for power factor correction are rated in
(a) kW (b) kVA
(c) kV (d) kVAR
Ans: d
29.In series resonant circuit, increasing inductance to its twice value and reducing capacitance to
its half value
(a) will change the maximum value of current at resonance
(b) will change the resonance frequency
(c) will change the impedance at resonance frequency
(d) will increase the selectivity of the circuit
Ans: d
30.Pure inductive circuit
(a)consumes some power on average
(b)does not take power at all from a line
(c)takes power from the line during some part of the cycle and then returns back to it during
other part of the cycle
(d)none of the above
Ans: c
31.Inductance affects the direct current flow
(a)only at the time of turning off (b)only at the time of turning on
(c)at the time of turning on and off (d)at all the time of operation
Ans: c
32.Inductance of a coil Varies
(a) directly as the cross-sectional area of magnetic core (b) directly as square of number of
turns
(c)directly as the permeability of the core (d)inversely as the length of the iron path
(e)as (a) to (d)
Ans: e
33.All the rules and laws of D.C. circuit also apply to A.C. circuit containing
(a)capacitance only (b)inductance only
(c)resistance only (d)all above
Ans: c
34.Time constant of an inductive circuit
(a)increases with increase of inductance and decrease of resistance
(b)increases with the increase of inductance and the increase of resistance
(c)increases with decrease of inductance and decrease of resistance
(d)increases with decrease of inductance and increase of resistance
Ans: a
35.Power factor of an inductive circuit is usually improved by connecting capacitor to it in
(a) parallel (b) series
(c) either (a) or (b) (d) none of the above
Ans: a
36.In a highly capacitive circuit the
(a) apparent power is equal to the actual power
(b) reactive power is more than the apparent power
(c) reactive power is more than the actual powetf
(d) actual power is more than its reactive power
Ans: c
37.Power factor of the following circuit will be zero
(a) resistance (b) inductance
(c) capacitance d) both (b) and (c)
Ans: d
38.Power factor of the following circuit will be unity
(a) inductance (b) capacitance
(c) resistance (d) both (a) and (b)
Ans: c
39.Power factor of the system is kept high
(a)to reduce line losses
(b)to maximise the utilization of the capacities of generators, lines and transformers
(c)to reduce voltage regulation of the line
(d)due to all above reasons
Ans: d
40.The time constant of the capacitance circuit is defined as the time during which voltage
(a) falls to 36.8% of its final steady value (b) rises to 38.6% of its final steady value
(c) rises to 63.2% of its final steady value (d) none of the above
Ans: c
41.In a loss-free R-L-C circuit the transient current is
(a) oscillating (b) square wave
(c) sinusoidal (d) non-oscillating
Ans: c
42.The r.m.s. value of alternating current is given by steady (D.C.) current which when flowing
through a given circuit for a given time produces
(a)the more heat than produced by A.C. when flowing through the same circuit
(b)the same heat as produced by A.C. when flowing through the same circuit
(c)the less heat than produced by A.C. flowing through the same circuit
(d)none of the above
Ans: b
43.The square waveform of current has following relation between r.m.s. value and average
value.
(a)r.m.s. value is equal to average value
(b)r.m.s. value of current is greater than average value
(c)r.m.s. value of current is less than average value
(d)none of the above
Ans: a
44.The double energy transient occur in the
(a)purely inductive circuit (b)R-L circuit
(c)R-C circuit (d) R-L-C circuit
Ans: d
45.The transient currents are associated with the
(a)changes in the stored energy in the inductors and capacitors
(b)impedance of the circuit
(c)applied voltage to the circuit
(d)resistance of the circuit
Ans: a
46.The power factor at resonance in R-L- C parallel circuit is
(a) zero (b) 0.08 lagging
(c) 0.8 leading (d) unity
Ans: d
47.In the case of an unsymmetrical alternating current the average value must always be taken
over
(a) unsymmetrical part of the wave form (b) the quarter cycle
(c) the half cycle (d) the whole cycle
Ans: d
48.In a pure resistive circuit
(a)current lags behind the voltage by 90° (b)current leads the voltage by 90°
(c)current can lead or lag the voltage by 90° (d) current is in phase with the voltage
Ans: d
49.In a pure inductive circuit
(a)the current is in phase with the voltage (b)the current lags behind the voltage by 90°
(c)the current leads the voltage by 90° (d)the current can lead or lag by 90°
Ans: b
50.In a circuit containing R, L and C, power loss can take place in
(a) C only (b) L only
(c) R only (d) all above
Ans: c
1. The insulating material for a cable should have (a) low cost (b) high dielectric strength (c) high mechanical strength (d) all of the above Ans: d 2. Which of the following protects a cable against mechanical injury ? (a) Bedding (b) Sheath (c) Armouring (d) None of the above Ans: c 3. Which of the following insulation is used in cables ? (a) Varnished cambric (b) Rubber (c) Paper (d) Any of the above Ans: d 4. Empire tape is (a) varnished cambric (b) vulcanised rubber (c) impregnated paper (d) none of the above Ans: a 5. The thickness of the layer of insulation on the conductor, in cables, depends upon (a) reactive power (b) power factor (c) voltage (d) current carrying capacity Ans: c 1.The S.I. unit of power is (a) henry (b) coulomb (c) watt (d) watt-hour Ans: c 2. Electric pressure is also called (a) resistance (b) power (c) voltage (d) energy Ans: c 3.The substances which have a large number of free electrons and offer a low resistance are called (a) insulators (b) inductors (c)semi-conductors (d)conductors Ans: d 4.Out of the following which is not a poor conductor ? (a) Cast iron (b) Copper (c) Carbon (d) Tungsten Ans: b 5.Out of the following which is an insulating material ? (a) Copper (b) Gold (c) Silver (d) Paper
Ans: d 1. Laminations of core are generally made of (a) case iron (b) carbon (c)silicon steel (d)stainless steel Ans: c 2. Which of the following could be lamina-proximately the thickness of lamina-tions of a D.C. machine ? (a)0.005 mm (b)0.05 mm (c)0.5 m (d)5 m Ans: c 3. The armature of D.C. generator is laminated to (a) reduce the bulk (b) provide the bulk (c)insulate the core (d)reduce eddy current loss Ans: d 4.The resistance of armature winding depends on (a) length of conductor (b) cross-sectional area of the conductor (c)number of conductors (d)all of the above Ans: d 5.The field coils of D.C. generator are usually made of (a) mica (b) copper (c) cast iron (d) carbon Ans: b 1. Kirchhoff s current law states that (a) net current flow at the junction is positive (b) Hebraic sum of the currents meeting at the junction is zero (c) no curreht can leave the junction without some current entering it. (d) total sum of currents meeting at the junction is zero Ans: b 2. According to Kirchhoffs voltage law, the algebraic sum of all IR drops and e.m.fs. in any closed loop of a network is always (a) negative (b) positive (c) determined by battery e.m.fs. (d) zero Ans: d 3. Kirchhoffs current law is applicable to only (a) junction in a network (b) closed loops in a network (c) electric circuits (d) electronic circuits Ans: a
4. Kirchhoffs voltage law is related to (a) junction currents (b) battery e.m.fs. (c) IR drops (d) both (b) and (c) (e) none of the above Ans: d 5. Superposition theorem can be applied only to circuits having (a) resistive elements (b) passive elements (c) non-linear elements (d) linear bilateral elements Ans: d 1.Speed of the stator field of an Induction motor is (a) Synchronous speed (b) Any speed (c) Less than Synchronous (d) Slip Speed Ans(a) Synchronous speed 2.Difference in speed between stator field and rotor (a) Full load speed (b)No load speed (c)Slip (d) Regulation Ans:(c)Slip 3.Frequency of current in rotor (a)Supply frequency (b)Less than supply frequency (c)Greater than supply frequency (d)Slip frequency Ans;(d) Slip Frequency 4. Shape of the torque slip curve is (a) Rectangular Hyperbola (b)Parabola (c)Sine
(d) Cosine Ans;(a) Rectangular Hyperbola 5.Machine with negative slip (a)Induction Motor (b) Brake (c)Induction Generator (d)Synchronous machine Ans(c) Induction Generator 1.The property of coil by which a counter e.m.f. is induced in it when the current through the coil changes is known as (a) self-inductance (b) mutual inductance (c) series aiding inductance (d) capacitance Ans: a 2.As per Faraday's laws of electromagnetic induction, an e.m.f. is induced in a conductor whenever it (a) lies perpendicular to the magnetic flux (b) lies in a magnetic field (e) cuts magnetic flux (d) moves parallel to the direction of the magnetic field Ans: c 3.Which of the following circuit element stores energy in the electromagnetic field ? (a) Inductance (b) Condenser (c) Variable resistor (d) Resistance Ans: a 4.The inductance of a coil will increase under all the following conditions except (a) when more length for the same number of turns is provided (6) when the number of turns of the coil increase (c) when more area for each turn is provided (d) when permeability of the core increases Ans: a 5. Higher the self-inductance of a coil, (a) lesser its weber-turns (b) lower the e.m.f. induced (c) greater the flux produced by it (d) longer the delay in establishing steady current. Ans: d 1. The converse of hardness is known as (a) malleability (b) toughness (c) softness (d) none of the above Ans: c 2. On which of the following factors does the resistivity of a material depend ? (a)Resistance of the conductor (b)Area of the conductor section (c)Length of the conductor (d) All of the above Ans: d
3. Is a negatively charged particle present in an atom. (a) Proton (b)Neutron (c)Electron (d) None of the above Ans: c 4. The formula ____ determines the number of electrons that can be accommodated in any level. (a) 2n2 (b)4n2 (c)2n3 (d)4ns Ans: a 5. The tiny block formed by the arrangement of a small group of atoms is called the (a) unit cell (b)space lattice (c)either (a) or (b) (d) none of the above Ans: a 1."The mass of an ion liberated at an electrode is directly proportional to the quantity of electricity". The above statement is associated with (a)Newton's law (b)Faraday's law of electromagnetic (c)Faraday's law of electrolysis (d)Gauss's law Ans: c 2.The charge required to liberate one gram equivalent of any substance is known as ______ constant (a) Time b) Faraday's (c) Boltzman Ans: b 3.During the charging of a lead-acid cell (a) its voltage increases (b) it gives out energy (c) its cathode becomes dark chocolate brown in colour (d) specific gravity of H2SO4 decreases Ans: a 4.The capacity of a lead-acid cell does not depend on its (a) temperature (b) rate of charge (c) rate of discharge (d) quantity of active material Ans: b 5.During charging the specific gravity of the electrolyte of a lead-acid battery (a) increases (b) decreases (c) remains the same (d) becomes zero Ans: a 1. Which of the following is an advantage of heating by electricity ? (a) Quicker operation (b) Higher efficiency (c) Absence of flue gases
(d) All of the above Ans: d 2. ________ has the highest value of thermal conductivity. (a) Copper (b) Aluminium (c) Brass (d) Steel Ans: a 3. Which of the following heating methods has maximum power factor ? (a) Arc heating (b) Dielectric heating (c) Induction heating (d) Resistance heating Ans: d 4 method has leading power factor (a) Resistance heating (b) Dielectric heating (c) Arc heating (d) Induction heating Ans: b 5 is used for heating non-conducting materials. (a) Eddy current heating (b) Arc heating (c) Induction heating (d) Dielectric heating Ans: d 1. An air gap is usually inserted in magnetic circuits to (a) increase m.m.f. (b) increase the flux (c) prevent saturation (d) none of the above Ans: c 2. The relative permeability of a ferromagnetic material is (a) less than one (b) more than one (c) more than 10 (d) more than 100 or 1000 Ans: d 3. The unit of magnetic flux is (a) henry
(b) weber (c) ampereturn/weber (d) ampere/metre Ans: b 4. Permeability in a magnetic circuit corresponds to______ in an electric circuit. (a) resistance (b) resistivity (c) conductivity (d) conductance Ans: c 5. Point out the wrong statement. Magnetic leakage is undesirable in electric machines because it (a) lowers their power efficiency (b) increases their cost of manufacture (c) leads to their increased weight (d) produces fringing Ans: a 1. An air gap is usually inserted in magnetic circuits to (a) increase m.m.f. (b) increase the flux (c) prevent saturation (d) none of the above Ans: c 2. The relative permeability of a ferromagnetic material is (a) less than one (b) more than one (c) more than 10 (d) more than 100 or 1000 Ans: d 3. The unit of magnetic flux is (a) henry (b) weber (c) ampereturn/weber (d) ampere/metre Ans: b 4. Permeability in a magnetic circuit corresponds to______ in an electric circuit. (a) resistance (b) resistivity (c) conductivity (d) conductance Ans: c
5. Point out the wrong statement. Magnetic leakage is undesirable in electric machines because it (a) lowers their power efficiency (b) increases their cost of manufacture (c) leads to their increased weight (d) produces fringing Ans: a 1. An air gap is usually inserted in magnetic circuits to (a) increase m.m.f. (b) increase the flux (c) prevent saturation (d) none of the above Ans: c 2. The relative permeability of a ferromagnetic material is (a) less than one (b) more than one (c) more than 10 (d) more than 100 or 1000 Ans: d 3. The unit of magnetic flux is (a) henry (b) weber (c) ampereturn/weber (d) ampere/metre Ans: b 4. Permeability in a magnetic circuit corresponds to______ in an electric circuit. (a) resistance (b) resistivity (c) conductivity (d) conductance Ans: c 5. Point out the wrong statement. Magnetic leakage is undesirable in electric machines because it (a) lowers their power efficiency (b) increases their cost of manufacture (c) leads to their increased weight (d) produces fringing Ans: a 1. An air gap is usually inserted in magnetic circuits to (a) increase m.m.f. (b) increase the flux (c) prevent saturation (d) none of the above
Ans: c 2. The relative permeability of a ferromagnetic material is (a) less than one (b) more than one (c) more than 10 (d) more than 100 or 1000 Ans: d 3. The unit of magnetic flux is (a) henry (b) weber (c) ampereturn/weber (d) ampere/metre Ans: b 4. Permeability in a magnetic circuit corresponds to______ in an electric circuit. (a) resistance (b) resistivity (c) conductivity (d) conductance Ans: c 5. Point out the wrong statement. Magnetic leakage is undesirable in electric machines because it (a) lowers their power efficiency (b) increases their cost of manufacture (c) leads to their increased weight (d) produces fringing Ans: a 1. An air gap is usually inserted in magnetic circuits to (a) increase m.m.f. (b) increase the flux (c) prevent saturation (d) none of the above Ans: c 2. The relative permeability of a ferromagnetic material is (a) less than one (b) more than one (c) more than 10 (d) more than 100 or 1000 Ans: d 3. The unit of magnetic flux is (a) henry (b) weber
(c) ampereturn/weber (d) ampere/metre Ans: b 4. Permeability in a magnetic circuit corresponds to______ in an electric circuit. (a) resistance (b) resistivity (c) conductivity (d) conductance Ans: c 5. Point out the wrong statement. Magnetic leakage is undesirable in electric machines because it (a) lowers their power efficiency (b) increases their cost of manufacture (c) leads to their increased weight (d) produces fringing Ans: a 1. An air gap is usually inserted in magnetic circuits to (a) increase m.m.f. (b) increase the flux (c) prevent saturation (d) none of the above Ans: c 2. The relative permeability of a ferromagnetic material is (a) less than one (b) more than one (c) more than 10 (d) more than 100 or 1000 Ans: d 3. The unit of magnetic flux is (a) henry (b) weber (c) ampereturn/weber (d) ampere/metre Ans: b 4. Permeability in a magnetic circuit corresponds to______ in an electric circuit. (a) resistance (b) resistivity (c) conductivity (d) conductance Ans: c 5. Point out the wrong statement.
Magnetic leakage is undesirable in electric machines because it (a) lowers their power efficiency (b) increases their cost of manufacture (c) leads to their increased weight (d) produces fringing Ans: a 1. An air gap is usually inserted in magnetic circuits to (a) increase m.m.f. (b) increase the flux (c) prevent saturation (d) none of the above Ans: c 2. The relative permeability of a ferromagnetic material is (a) less than one (b) more than one (c) more than 10 (d) more than 100 or 1000 Ans: d 3. The unit of magnetic flux is (a) henry (b) weber (c) ampereturn/weber (d) ampere/metre Ans: b 4. Permeability in a magnetic circuit corresponds to______ in an electric circuit. (a) resistance (b) resistivity (c) conductivity (d) conductance Ans: c 5. Point out the wrong statement. Magnetic leakage is undesirable in electric machines because it (a) lowers their power efficiency (b) increases their cost of manufacture (c) leads to their increased weight (d) produces fringing Ans: a 1. An air gap is usually inserted in magnetic circuits to (a) increase m.m.f. (b) increase the flux (c) prevent saturation (d) none of the above Ans: c
2. The relative permeability of a ferromagnetic material is (a) less than one (b) more than one (c) more than 10 (d) more than 100 or 1000 Ans: d 3. The unit of magnetic flux is (a) henry (b) weber (c) ampereturn/weber (d) ampere/metre Ans: b 4. Permeability in a magnetic circuit corresponds to______ in an electric circuit. (a) resistance (b) resistivity (c) conductivity (d) conductance Ans: c 5. Point out the wrong statement. Magnetic leakage is undesirable in electric machines because it (a) lowers their power efficiency (b) increases their cost of manufacture (c) leads to their increased weight (d) produces fringing Ans: a 1. Which of the following are the applications of D.C. system ? (a) Battery charging work (b) Arc welding (c) Electrolytic and electro-chemical processes (d) Arc lamps for search lights (e) All of the above Ans: e 2. Which of the following methods may be used to convert A.C. system to D.C. ? (a) Rectifiers (b) Motor converters (c) Motor-generator sets (d) Rotary converters (e) All of the above Ans: e 3. In a single phase rotary converter the number of slip rings will be (a) two (b) three (c) four (d) six (e) none Ans: a 4. A synchronous converter can be started
(a) by means of a small auxiliary motor (b) from AC. side as induction motor (c) from D.C. side as D.C. motor (d) any of the above methods (e) none of the above methods Ans: d 5. A rotary converter is a single machine with (a) one armature and one field (b) two armatures and one field (c) one armature and two fields (d) none of the above Ans: a 1. By which of the following systems electric power may be transmitted ? (a) Overhead system (b) Underground system (c) Both (a) and (b) (d) None of the above Ans: c 2 are the conductors, which connect the consumer's terminals to the distribution (a) Distributors (b) Service mains (c) Feeders (d) None of the above Ans: b 3. The underground system cannot be operated above (a) 440 V (b) 11 kV (c) 33 kV (d) 66 kV Ans: d 4. Overhead system can be designed for operation upto (a) 11 kV (b) 33 kV (c) 66 kV (d) 400 kV Ans: c 5. If variable part of annual cost on account of interest and depreciation on the capital outlay is equal to the annual cost of electrical energy wasted in the conductors, the total annual cost will be minimum and the corresponding size of conductor will be most economical. This statement is known as (a) Kelvin's law (b) Ohm's law (c) Kirchhoffs law (d) Faraday's law (e) none of the above Ans: a 1. In an open loop control system
(a) Output is independent of control input (b) Output is dependent on control input
(c) Only system parameters have effect on the control output
(d) None of the above
Ans: a
2. For open control system which of the following statements is incorrect ?
(a) Less expensive
(b) Recalibration is not required for maintaining the required quality of the output
(c) Construction is simple and maintenance easy
(d) Errors are caused by disturbances
Ans: b
3. A control system in which the control action is somehw dependent on the output is known as
(a) Closed loop system (b)Semiclosed loop system (c)Open system (d)None of the above
Ans: a
4. In closed loop control system, with positive value of feedback gain the overall gain of the
system will
(a) decrease (b) increase (c) be unaffected (d) any of the above
Ans: a
5. Which of the following is an open loop control system ?
(a) Field controlled D.C. motor (b) Ward leonard control (c)Metadyne (d)Stroboscope
Ans: a
6. Which of the following statements is not necessarily correct for open control system ?
(a) Input command is the sole factor responsible for providing the control action
(b) Presence of non-linearities causes malfunctioning
(c) Less expensive
(d) Generally free from problems of non-linearities
Ans: b
7. In open loop system
(a) the control action depends on the size of the system
(b) the control action depends on system variables
(c) the control action depends on the input signal
(d) the control action is independent of the output
Ans: d
8 has tendency to oscillate.
(a) Open loop system (b)Closed loop system (c) Both (a) and (b) (d)Neither (a) nor (b)
Ans: b
9. A good control system has all the following features except
(a) good stability (b) slow response (c) good accuracy (d) sufficient power handling capacity
Ans: b
10. A car is rtyining at a constant speed of 50 km/h, which of the following is the feedback
element for the driver ?
(a) Clutch (b) Eyes (c) Needle of the speedometer (d)Steering wheel (e)None of the above
Ans: c
11. The initial response when tne output is not equal to input is called
(a) Transient response (b)Error response (c) Dynamic response (d) Either of the above
Ans: a
12. A control system working under unknown random actions is called
(a) computer control system (b) digital data system
(c) stochastic control system (d) adaptive control system
Ans: c
13. An automatic toaster is a ______ loop control system.
(a) open (b) closed (c) partially closed (d) any of the above
Ans: a
14. Any externally introduced signal affecting the controlled output is called a
(a) feedback (b) stimulus (c) signal (d) gain control
Ans: b
15. A closed loop system is distinguished from open loop system by which of the following ?