| Three 6 ohm resistors are connected to form a triangle. What is the resistance between any two corners ___________? |
| A. 3/2 Q B. 6 Q C. 4 Q D. 8/3 Q |
| Which method can be used for absolute measurement of resistances _______________? |
| A. Lorentz method B. Releigh method C. Ohm’s law method D. Wheatstone bridge method |
| Ohm’s law is not applicable to__________? |
| A. semi-conductors B. D. C. circuits C. small resistors D. high currents |
| Two copper conductors have equal length. The cross-sectional area of one conductor is four times that of the other. If the conductor having smaller cross-sectional area has a resistance of 40 ohms the resistance of other conductor will be_____________? |
| A. 160 ohms B. 80 ohms C. 20 ohms D. 10 ohms |
| A nichrome wire used as a heater coil has the resistance of 2 £2/m. For a heater of 1 kW at 200 V, the length of wire required will be_____________? |
| A. 80 m B. 60 m C. 40 m D. 20 m |
| Temperature co-efficient of resistance is expressed in terms of___________? |
| A. ohms/°C B. mhos/ohm°C C. ohms/ohm°C D. mhos/°C |
| When current flows through heater coil it glows but supply wiring does not glow because______________? |
| A. current through supply line flows at slower speed B. supply wiring is covered with insulation layer C. resistance of heater coil is more than the supply wires D. supply wires are made of superior material |
| The condition for the validity under Ohm’s law is that_______________? |
| A. resistance must be uniform B. current should be proportional to the size of the resistance C. resistance must be wire wound type D. temperature at positive end should be more than the temperature at negative end |
| Which of the following statement is correct_______________? |
| A. A semi-conductor is a material whose conductivity is same as between that of a conductor and an insulator B. A semi-conductor is a material which has conductivity having average value of conductivity of metal and insulator C. A semi-conductor is one which con¬ducts only half of the applied voltage D. A semi-conductor is a material made of alternate layers of conducting material and insulator |
| A rheostat differs from potentiometer in the respect that it_____________? |
| A. has lower wattage rating B. has higher wattage rating C. has large number of turns D. offers large number of tapping |
| An open resistor, when checked with an ohm-meter reads_____________? |
| A. zero B. infinite C. high but within tolerance D. low but not zero |
| are the materials having electrical conductivity much less than most of the metals but much greater than that of typical insulators______________? |
| A. Varistors B. Thermistor C. Semi-conductors D. Variable resistors |
| All good conductors have high____________? |
| A. conductance B. resistance C. reluctance D. thermal conductivity |
| Voltage dependent resistors are usually made from________________? |
| A. Charcoal B. Silicon Carbide C. Nichrome D. Graphite |
| Voltage dependent resistors are used_____________? |
| A. for inductive circuits B. to supress surges C. as heating elements D. as current stabilizers |
| The ratio of mass of proton to that of electron is nearly_____________? |
| A. 1840 B. 1840 C. 30 D. 4 |
| The number of electrons in the outer most orbit of carbon atom is___________? |
| A. 3 B. 4 C. 6 D. 7 |
| With three resistances connected in parallel, if each dissipates 20 W the total power supplied by the voltage source equals_____________? |
| A. 10 W B. 20 W C. 40 W D. 60 W |
| A thermistor has_____________? |
| A. positive temperature coefficient B. negative temperature coefficient C. zero temperature coefficient D. variable temperature coefficient |
| If/, R and t are the current, resistance and time respectively, then according to Joule’s law heat produced will be proportional to_______________? |
| A. I2Rt B. I2Rf C. I2R2t D. I2R2t* |
| Nichrome wire is an alloy of_____________? |
| A. lead and zinc B. chromium and vanadium C. nickel and chromium D. copper and silver |
| When a voltage of one volt is applied, a circuit allows one micro ampere current to flow through it. The conductance of the circuit is___________? |
| A. 1 n-mho B. 106 mho C. 1 milli-mho D. none of the above |
| Which of the following can have negative temperature coefficient _____________? |
| A. Compounds of silver B. Liquid metals C. Metallic alloys D. Electrolytes |
| Conductance : mho :: ____________? |
| A. resistance : ohm B. capacitance : henry C. inductance : farad D. lumen : steradian |
| 1 angstrom is equal to______________? |
| A. 10-8 mm B. 10″6 cm C. 10″10 m D. 10~14 m |
| One newton meter is same as_____________? |
| A. one watt B. one joule C. five joules D. one joule second |
| Which of the following does not change in a transformer ? |
| A. Current B. Voltage C. Frequency D. All of the above |
| In a transformer the energy is conveyed from primary to secondary_________? |
| A. through cooling coil B. through air C. by the flux D. none of the above |
| A transformer core is laminated to__________? |
| A. reduce hysteresis loss B. reduce eddy current losses C. reduce copper losses D. reduce all above losses |
| The degree of mechanical vibrations produced by the laminations of a transformer depends on____________? |
| A. tightness of clamping B. gauge of laminations C. size of laminations D. all of the above |
| The no-load current drawn by transformer is usually what per cent of the full-load current ? |
| A. 0.2 to 0.5 per cent B. 2 to 5 per cent C. 12 to 15 per cent D. 20 to 30 per cent |
| The path of a magnetic flux in a transformer should have______________? |
| A. high resistance B. high reluctance C. low resistance D. low reluctance |
| No-load on a transformer is carried out to determine______________? |
| A. copper loss B. magnetising current C. magnetising current and loss D. efficiency of the transformer |
| The dielectric strength of transformer oil is expected to be______________? |
| A. lkV B. 33 kV C. 100 kV D. 330 kV |
| Sumpner’s test is conducted on transformers to determine_____________? |
| A. temperature B. stray losses C. all-day efficiency D. none of the above |
| The permissible flux density in case of cold rolled grain oriented steel is around__________? |
| A. 1.7 Wb/m2 B. 2.7 Wb/m2 C. 3.7 Wb/m2 D. 4.7 Wb/m2 |
| The efficiency of a transformer will be maximum when_____________? |
| A. copper losses = hysteresis losses B. hysteresis losses = eddy current losses C. eddy current losses = copper losses D. copper losses = iron losses |
| No-load current in a transformer________________? |
| A. lags behind the voltage by about 75° B. leads the voltage by about 75° C. lags behind the voltage by about 15° D. leads the voltage by about 15° |
| The purpose of providing an iron core in a transformer is to_____________? |
| A. provide support to windings B. reduce hysteresis loss C. decrease the reluctance of the magnetic path D. reduce eddy current losses |
| Which of the following is not a part of transformer installation ? |
| A. Conservator B. Breather C. Buchholz relay D. Exciter |
| While conducting short-circuit test on a transformer the following side is short circuited? |
| A. High voltage side B. Low voltage side C. Primary side D. Secondary side |
| In the transformer following winding has got more cross-sectional area______________? |
| A. Low voltage winding B. High voltage winding C. Primary winding D. Secondary winding |
| A transformer transforms__________________? |
| A. voltage B. current C. power D. frequency |
| A transformer cannot raise or lower the voltage of a D.C. supply because_______________? |
| A. there is no need to change the D.C. voltage B. a D.C. circuit has more losses C. Faraday’s laws of electromagnetic induction are not valid since the rate of change of flux is zero D. none of the above |
| Primary winding of a transformer________________? |
| A. is always a low voltage winding B. is always a high voltage winding C. could either be a low voltage or high voltage winding D. none of the above |
| Which winding in a transformer has more number of turns ? |
| A. Low voltage winding B. High voltage winding C. Primary winding D. Secondary winding |
| Efficiency of a power transformer is of the order of________________? |
| A. 100 per cent B. 98 per cent C. 50 per cent D. 25 per cent |
| In a given transformer for given applied voltage, losses which remain constant irrespective of load changes are______________? |
| A. friction and windage losses B. copper losses C. hysteresis and eddy current losses D. none of the above |
| A common method of cooling a power transformer is_______________? |
| A. natural air cooling B. air blast cooling C. oil cooling D. any of the above |
| The no load current in a transformer lags behind the applied voltage by an angle of about_____________? |
| A. 180° B. 120″ C. 90° D. 75° |
| In a transformer routine efficiency depends upon_____________? |
| A. supply frequency B. load current C. power factor of load D. both B. and (c) |
| In the transformer the function of a conservator is to_______________? |
| A. provide fresh air for cooling the transformer B. supply cooling oil to transformer in time of need C. protect the transformer from damage when oil expends due to heating D. none of the above |
| Natural oil cooling is used for transformers up to a rating of____________? |
| A. 3000 kVA B. 1000 kVA C. 500 kVA D. 250 kVA |
| Power transformers are designed to have maximum efficiency at___________? |
| A. nearly full load B. 70% full load C. 50% full load D. no load |
| The maximum efficiency of a distribution transformer is____________? |
| A. at no load B. at 50% full load C. at 80% full load D. at full load |
| Transformer breaths in when_______________? |
| A. load on it increases B. load on it decreases C. load remains constant D. none of the above |
| No-load current of a transformer has_____________? |
| A. has high magnitude and low power factor B. has high magnitude and high power factor C. has small magnitude and high power factor D. has small magnitude and low power factor |
| Spacers are provided between adjacent coils? |
| A. to provide free passage to the cooling oil B. to insulate the coils from each other C. both A. and (b) D. none of the above |
| Greater the secondary leakage flux____________? |
| A. less will be the secondary induced e.m.f. B. less will be the primary induced e.m.f. C. less will be the primary terminal voltage D. none of the above |
| The purpose of providing iron core in a step-up transformer is? |
| A. to provide coupling between primary and secondary B. to increase the magnitude of mutual flux C. to decrease the magnitude of mag-netizing current D. to provide all above features |
| The power transformer is a constant______________? |
| A. voltage device B. current device C. power device D. main flux device |
| Two transformers operating in parallel will share the load depending upon their____________? |
| A. leakage reactance B. per unit impedance C. efficiencies D. ratings |
| If R2 is the resistance of secondary winding of the transformer and K is the transformation ratio then the equivalent secondary resistance referred to primary will be___________? |
| A. R2/VK B. R2IK2 C. R22!K2 D. R22/K |
| If the percentage impedances of the two transformers working in parallel are different, then______________________? |
| A. transformers will be overheated B. power factors of both the transformers will be same C. parallel operation will be not possible D. parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load |
| What will happen if the transformers working in parallel are not connected with regard to polarity ? |
| A. The power factor of the two trans-formers will be different from the power factor of common load B. Incorrect polarity will result in dead short circuit C. The transformers will not share load in proportion to their kVA ratings D. none of the above |
| In a transformer the tappings are generally provided on_____________? |
| A. primary side B. secondary side C. low voltage side D. high voltage side |
| The use of higher flux density in the transformer design____________? |
| A. reduces weight per kVA B. reduces iron losses C. reduces copper losses D. increases part load efficiency |
| The chemical used in breather for transformer should have the quality of____________? |
| A. ionizing air B. absorbing moisture C. cleansing the transformer oil D. cooling the transformer oil |
| The chemical used in breather is_______________? |
| A. asbestos fiber B. silica sand C. sodium chloride D. silica gel |
| An ideal transformer has infinite values of primary and secondary inductances. The statement is______________? |
| A. true B. false |
| The transformer ratings are usually expressed in terms of______________? |
| A. volts B. amperes C. kW D. kVA |
| The noise resulting from vibrations of laminations set by magnetic forces, is termed as_________________? |
| A. magnetostrication B. boo C. hum D. zoom |
| Hysteresis loss in a transformer varies as CBmax = maximum flux density) ? |
| A. Bmax B. Bmax1-6 C. Bmax1-83 D. B max |
| Material used for construction of transformer core is usually___________________? |
| A. wood B. copper C. aluminium D. silicon steel |
| The thickness of laminations used in a transformer is usually____________? |
| A. 0.4 mm to 0.5 mm B. 4 mm to 5 mm C. 14 mm to 15 mm D. 25 mm to 40 mm |
| The function of conservator in a transformer is___________________? |
| A. to project against’internal fault B. to reduce copper as well as core losses C. to cool the transformer oil D. to take care of the expansion and contraction of transformer oil due to variation of temperature of sur-roundings |
| Helical coils can be used on___________? |
| A. low voltage side of high kVA transformers B. high frequency transformers C. high voltage side of small capacity transformers D. high voltage side of high kVA rating transformers |
| Harmonics in transformer result in___________? |
| A. increased core losses B. increased I2R losses C. magnetic interference with communication circuits D. all of the above |
| In a transformer the resistance between its primary and secondary is____________? |
| A. zero B. 1 ohm C. 1000 ohms D. infinite |
| The core used in high frequency transformer is usually___________? |
| A. copper core B. cost iron core C. air core D. mild steel core |
| A transformer oil must be free from________________? |
| A. sludge B. odour C. gases D. moisture |
| A Buchholz relay can be installed on______________? |
| A Buchholz relay can be installed on A. auto-transformers B. air-cooled transformers C. welding transformers D. oil cooled transformers |
| The full-load copper loss of a trans¬former is 1600 W. At half-load, the copper loss will be___________? |
| A. 6400 W B. 1600 W C. 800 W D. 400 W |
| Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds? |
| A. 50°C B. 80°C C. 100°C D. 150°C |
| The main reason for generation of harmonics in a transformer could be_______________? |
| A. fluctuating load B. poor insulation C. mechanical vibrations D. saturation of core |
| The value of flux involved m the e.m.f. equation of a transformer is____________? |
| A. average value B. r.m.s. value C. maximum value D. instantaneous value |
| Distribution transformers are generally designed for maximum efficiency around________________? |
| A. 90% load B. zero load C. 25% load D. 50% load |
| Which of the following property is not necessarily desirable in the material for transformer core ? |
| A. Mechanical strength B. Low hysteresis loss C. High thermal conductivity D. High permeability |
| Star/star transformers work satisfactorily when________________? |
| A. load is unbalanced only B. load is balanced only C. on balanced as well as unbalanced loads D. none of the above |
| Delta/star transformer works satisfactorily when______________? |
| A. load is balanced only B. load is unbalanced only C. on balanced as well as unbalanced loads D. none of the above |
| Silicon steel used in lamination’s mainly reduces___________? |
| A. hysteresis loss B. eddy current losses C. copper losses D. all of the above |
| Which winding of the transformer has less cross-sectional area? |
| A. Primary winding B. Secondary winding C. Low voltage winding D. High voltage winding |
| Power transformers are generally designed to have maximum efficiency around__________? |
| A. no-load B. half-load C. near full-load D. 10% overload |
| Which of the following is the main advantage of an auto-transformer over a two winding transformer? |
| A. Hysteresis losses are reduced B. Saving in winding material C. Copper losses are negligible D. Eddy losses are totally eliminated |
| During short circuit test iron losses are negligible because of _____________? |
| A. the current on secondary side is negligible B. the voltage on secondary side does not vary C. the voltage applied on primary side is low D. full-load current is not supplied to the transformer |
| Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in____________? |
| A. short-circuiting of the secondaries B. power factor of one of the transformers is leading while that of the other lagging C. transformers having higher copper losses will have negligible core losses D. loading of the transformers not in proportion to their kVA ratings |
| Buchholz’s relay gives warning and protection against_________________? |
| A. electrical fault inside the transformer itself B. electrical fault outside the transformer in outgoing feeder C. for both outside and inside faults D. none of the above |
| The magnetising current of a transformer is usually small because it has___________? |
| A. small air gap B. large leakage flux C. laminated silicon steel core D. fewer rotating parts |
| The changes in volume of transformer cooling oil due to variation of atmospheric temperature during day and night is taken care of by which part of transformer? |
| A. Conservator B. Breather C. Bushings D. Buchholz relay |
| Which of the following does not change in an ordinary transformer ? |
| A. Frequency B. Voltage C. Current D. Any of the above |
| An ideal transformer is one which has_____________? |
| A. no losses and magnetic leakage B. interleaved primary and secondary windings C. a common core for its primary and secondary windings D. core of stainless steel and winding of pure copper metal E. none of the above |
| The leakage flux in a transformer depends upon______________? |
| A. load current B. load current and voltage C. load current, voltage and frequency D. load current, voltage, frequency and power factor |
| Which of the following properties is not necessarily desirable for the material for transformer core ? |
| A. Low hysteresis loss B. High permeability C. High thermal conductivity D. Adequate mechanical strength |
| When a given transformer is run at its rated voltage but reduced frequency, its____________? |
| A. flux density remains unaffected B. iron losses are reduced C. core flux density is reduced D. core flux density is increased |
| The path of the magnetic flux in transformer should have____________? |
| A. high reluctance B. low reactance C. high resistance D. low resistance |
| In an actual transformer the iron loss remains practically constant from no load to full load because:____________? |
| A. value of transformation ratio remains constant B. permeability of transformer core remains constant C. core flux remains practically constant D. primary voltage remains constant C. secondary voltage remains constant |
| Noise level test in a transformer is a______________? |
| A. special test B. routine test C. type test D. none of the above |
| A transformer can have zero voltage regulation at______________? |
| A. leading power factor B. lagging power factor C. unity power factor D. zero power factor |
| An ideal transformer will have maximum efficiency at a load such that? |
| A. copper loss = iron loss B. copper loss iron loss D. none of the above |
| Which of the following is not a routine test on transformers ? |
| A. Core insulation voltage test B. Impedance test C. Radio interference test D. Polarity test |
| If the supply frequency to the transformer is increased,”the iron loss will__________? |
| A. not change B. decrease C. increase D. any of the above |
| Helical coils can be used on___________________? |
| A. low voltage side of high kVA transformers B. high frequency transformers C. high voltage side of small capacity transformers D. high voltage side of high kVA rating transformers |
| Negative voltage regulation is indicative that the load is___________? |
| A. capacitive only B. inductive only C. inductive or resistive D. none of the above |
| Which of the following loss in a transformer is zero even at full load ____________? |
| A. Core loss B. Friction loss C. Eddy current loss D. Hysteresis loss |
| Iron loss of a transformer can be measured by____________? |
| A. low power factor wattmeter B. unity power factor wattmeter C. frequency meter D. any type of wattmeter |
| Which of the following is the most likely source of harmonics in a transformer ? |
| A. poor insulation B. Overload C. loose connections D. Core saturation |
| If a transformer is continuously operated the maximum temperature rise will occur in_______________? |
| A. core B. windings C. tank D. any of the above |
| The hum in a transformer is mainly attributed to______________? |
| A. load changes B. oil in the transformer C. magnetostriction D. mechanical vibrations |
| The maximum load that a power transformer can carry is limited by its________________? |
| A. temperature rise B. dielectric strength of oil C. voltage ratio D. copper loss |
| The efficiency of a transformer, under heavy loads, is comparatively low because_______________? |
| A. copper loss becomes high in proportion to the output B. iron loss is increased considerably C. voltage drop both in primary and secondary becomes large D. secondary output is much less as compared to primary input |
| When secondary of a current transformer is open-circuited its iron core will be__________? |
| A. hot because of heavy iron losses taking place in it due to high flux density B. hot because primary will carry heavy current C. cool as there is no secondary current D. none of above will happen |
| The transformer lamination’s are insulated from each other by____________? |
| A. mica strip B. thin coat of varnish C. paper D. any of the above |
| An open-circuit test on a transformer is conducted primarily to measure______________? |
| A. insulation resistance B. copper loss C. core loss D. total loss E. efficiency F. none of the above |
| Which type of winding is used in 3 phase shell-type transformer? |
| A. Circular type B. Sandwich type C. Cylindrical type D. Rectangular type |
| A no-load test is performed on a transformer to determine_______________? |
| A. core loss B. copper loss C. efficiency D. magnetising current E. magnetising current and loss |
| The voltage transformation ratio of a transformer is equal to the ratio of_______________? |
| A. primary turns to secondary turns B. secondary current to primary current C. secondary induced e.m.f. to primary induced e.m.f D. secondary terminal voltage to primary applied voltage |
| During open circuit test of a transformer: |
| A. primary is supplied rated voltage B. primary is supplied full-load current C. primary is supplied current at reduced voltage D. primary is supplied rated kVA |
| Part of the transformer which is most subject to damage from overheating is_____________? |
| A. iron core B. copper winding C. winding insulation D. frame or case E. transformer tank |
| Open circuit test on transformers is conducted to determine____________? |
| A. hysteresis losses B. copper losses C. core losses D. eddy current losses |
| If a transformer is switched on to a voltage more than the rated voltage______________? |
| A. its power factor will deteriorate B. its power factor will increase C. its power factor will remain unaffected D. its power factor will be zero |
| Short circuit test on transformers is conducted to determine____________? |
| A. hysteresis losses B. copper losses C. core losses D. eddy current losses |
| Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is_________________? |
| A. approximately equal to one B. less than one C. great than one D. none of the above |
| Minimum voltage regulation occurs when the power factor of the load is_____________? |
| A. unity B. lagging C. leading D. zero |
| For the parallel operation of single phase transformers it is necessary that they should have___________? |
| A. same efficiency B. same polarity C. same kVA rating D. same number of turns on the secondary side. |
| In a step-down transformer, there is a change of 15 A in the load current. This results in change of supply current of_________________? |
| A. less than 15 A B. more than 15 A C. 15 A D. none of the above |
| The transformer oil should have _______ volatility and _______ viscosity? |
| A. low,low B. high,high C. low,high D. high,low |
| The efficiencies of transformers compared with that of electric motors of the same power are____________? |
| A. about the same B. much smaller C. much higher D. somewhat smaller E. none of the above |
| The function of breather in a transformer is___________? |
| A. to provide oxygen inside the tank B. to cool the coils during reduced load C. to cool the transformer oil D. to arrest flow of moisture when outside air enters the transformer |
| The secondary winding of which of the following transformers is always kept closed? |
| A. Step-up transformer B. Step-down transformer C. Potential transformer D. Current transformer |
| The size of a transformer core will depend on__________? |
| A. frequency B. area of the core C. flux density of the core material D. A. and B. both |
| N atural air coo ling is generally restricted for transformers up to__________? |
| A. 1.5 MVA B. 5 MVA C. 15 MVA D. 50 MVA |
| A shell-type transformer has_________? |
| A. high eddy current losses B. reduced magnetic leakage C. negligibly hysteresis losses D. none of the above |
| The secondary of a current transformer is always short-circuited under operating conditions because it____________________? |
| A. avoids core saturation and high voltage induction B. is safe to human beings C. protects the primary circuit D. none of the above |
| In a transformer the resistance between its primary and secondary should be_____________? |
| A. zero B. 10 Q C. 1000 Q D. infinity |
| A transformer can have regulation closer to zero___________? |
| A. on full-load B. on overload C. on leading power factor D. on zero power factor |
| A Transformer transforms____________? |
| A. voltage B. current C. current and voltage D. power |
| For a transformer, operating at constant load current, maximum efficiency will occur at______________? |
| A. 0.8 leading power factor B. 0.8 lagging power factor C. zero power factor D. unity power factor |
| Which of the following protection is normally not provided on small distribution transformers ? |
| A. Overfluxing protection B. Buchholz relay C. Overcurrent protection D. All of the above |
| A good voltage regulation of a transformer means________________? |
| A good voltage regulation of a transformer means A. output voltage fluctuation from no load to full load is least B. output voltage fluctuation with power factor is least C. difference between primary and secondary voltage is least D. difference between primary and secondary voltage is maximum |
| Which of the following acts as a protection against high voltage surges due to lightning and switching ? |
| A. Horn gaps B. Thermal overload relays C. Breather D. Conservator |
| The efficiency of two identical transformers under load conditions can be determined by_______________? |
| A. short-circuit test B. back-to-back test C. open circuit test D. any of the above |
| Which of the following insulating materials can withstand the highest temperature safely ? |
| A. Cellulose B. Asbestos C. Mica D. Glass fibre |
| Which of the following parts of a transformer is visible from outside ? |
| A. Bushings B. Core C. Primary winding D. Secondary winding |
| The noise produced by a transformer is termed as_______________________? |
| A. zoom B. hum C. ringing D. buzz |
| Reduction in core losses and increase in permeability are obtained with transformer employing__________? |
| A. core built-up of laminations of cold rolled grain oriented steel B. core built-up of laminations of hot rolled sheet C. either of the above D. none of the above |
| In a power or distribution transformer about 10 per cent end turns are heavily insulated__________? |
| A. to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns B. to absorb the line surge voltage and save the winding of transformer from damage C. to reflect the line surge and save the winding of a transformer from damage D. none of the above |
| For given applied voltage, with the increase in frequency of the applied voltage? |
| A. eddy current loss will decrease B. eddy current loss will increase C. eddy current loss will remain unchanged D. none of the above |
| Losses which occur in rotating electric machines and do not occur in transformers are___________? |
| A. friction and windage losses B. magnetic losses C. hysteresis and eddy current losses D. copper losses |
| In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are__________? |
| A. hysteresis and eddy current losses B. friction and windage losses C. copper losses D. none of the above |
| Which of the following statements regarding an idel single-phase transformer having a turn ratio of 1 : 2 and drawing a current of 10 A from 200 V A.C. supply is incorrect? |
| A. Its secondary current is 5 A B. Its secondary voltage is 400 V C. Its rating is 2 kVA D. Its secondary current is 20 A E. It is a step-up transformer |
| Which of the following relays is used on long transmission lines? |
| A. Impedance relay B. Mho’s relay C. Reactance relay D. None of the above |
| The steel used in steel cored conductors is usually__________? |
| A. alloy steel B. stainless steel C. mild steel D. high speed steel E. all of the above |
| Which of the following distribution systems is more reliable? |
| A. Radial system B. Tree system C. Ring main system D. All are equally reliable |
| Which of the following characteristics should the line supports for transmission lines possess? |
| A. Low cost B. High mechanical strength C. Longer life D. All of the above |
| Transmission voltage of 11 kV is normally used for distances up to_____km? |
| A. 20—25 km B. 40—50 km C. 60—70 km D. 80—100 km |
| A conductor, due to sag between two supports, takes the form of____________? |
| A. semi-circle B. triangle C. ellipse D. catenary |
| In AC.S.R. conductors, the insulation between aluminium and steel conductors is_________? |
| A. insulin B. bitumen C. varnish D. no insulation is required |
| Which of the following bus-bar schemes has the lowest cost? |
| A. Ring bus-bar scheme B. Single bus-bar scheme C. Breaker and a half scheme D. Main and transfer scheme |
| Owing to skin effect: |
| A. current flows through the half cross-section of the conductor B. portion of the conductor near the surface carries more current and core of the conductor carries less current C. portion of the conductor near the surface carries less current and core of the conductor carries more cur¬rent D. any of the above E. none of the above |
| By which of the following methods string efficiency can be improved? |
| A. Using a guard ring B. Grading the insulator C. Using long cross arm D. Any of the above E. None of the above |
| In aluminium conductors, steel core is provided to____________? |
| A. compensate for skin effect B. neutralise proximity effect C. reduce line inductance D. increase the tensile strength |
| By which of the following a bus-bar is rated? |
| A. Current only B. Current and voltage C. Current, voltage and frequency D. Current, voltage, frequency and short time current |
| A circuit is disconnected by isolators when____________? |
| A. line is energized B. there is no current in the line C. line is on full load D. circuit breaker is not open |
| For which of the following equipment current rating is not necessary? |
| A. Circuit breakers B. Isolators C. Load break switch D. Circuit breakers and load break switches |
| In a substation the following equipment is not installed? |
| A. exciters B. series capacitors C. shunt reactors D. voltatre transformers |
| jCorona usually occurs when the electrostatic stress in air around the conductor exceeds? |
| A. 6.6 kV (r.m.s. value)/cm B. 11 kV (r.m.s. value)/cm C. 22 kV (maximum value)/cm D. 30 kV (maximum value)/cm |
| The voltage drop, for constant voltage transmission is compensated by installing__________? |
| A. inductors B. capacitors C. synchronous motors D. all of above E. none of the above |
| The use of strain type insulators is made where the conductors are__________? |
| A. dead ended B. at intermediate anchor towers C. any of the above D. none of the above |
| The current drawn by the line due to corona losses is___________? |
| A. non-sinusoidal B. sinusoidal C. triangular D. square |
| Pin type insulators are generally not used for voltages beyond_________? |
| A. 1 kV B. 11 kV C. 22 kV D. 33 kV |
| Aluminium has a specific gravity of___________? |
| A. 1.5 B. 2.7 C. 4.2 D. 7.8 |
| For transmission of power over a distance of 200 km, the transmission voltage should be_________kv? |
| A. 132 kV B. 66 kV C. 33 kV D. 11 kV |
| For aluminum, as compared to copper, all the following factors have higher values except: |
| A. specific volume B. electrical conductivity C. coefficient of linear expansion D. resistance per unit length for the same cross-section |
| Which of the following equipment, for regulating the voltage in distribution feeder, will be most economical? |
| A. Static condenser B. Synchronous condenser C. Tap changing transformer D. Booster transformer |
| In a tap changing transformer, the tappings are provided on__________? |
| A. primary winding B. secondary winding C. high voltage winding D. any of the above |
| Constant voltage transmission entails the following disadvantage? |
| A. large conductor area is required for same power transmission B. short-circuit current of the system is increased C. either of the above D. none of the above |
| On which of the following factors skin effect depends? |
| A. Frequency of the current B. Size of the conductor C. Resistivity of the conductor material D. All of the above |
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