Current Electricity (Generation, Transmission, Distribution & Utilization)
Capacitors
Electromagnetic Induction
Electrolysis and Storage of Batteries
Principle of DC and AC current
DC Generators and DC Motors
Transformers & Induction Motors
Alternators
Semi‐conductors & Electronics
Measuring Equipment
Protection and switch gear
Air conditioning
Contents:
Ques 1. The flow of current in solids is due to a. Electrons
b. Electrons & Ions c. Atoms
d. Nucleus Answer: a
Ques 2. Electric current in a wire is the flow of………. electrons?
a. Free b. Valence c. Bound d. Loose Answer: a
Ques 3. Electromotive force in a circuit a. Causes free electrons to flow b. Increases the circuit resistance c. Maintains circuit resistance
d. Is needed to make the circuit complete Answer: a
Ques 4. The resistance of a material is………. its area of cross section.
a. Directly proportional b. Independent of
c. Inversely proportional to d. Equal to
Answer: c
Ques 5. If the length and area of cross section of a wire are doubled, then its resiatnce a. Becomes 4 times
b. Becomes 6 times c. Remains same d. Becomes 2 times Answer: c
Ques 6. What is the SI unit of specific resistance or resistivity?
a. Ohm – circular per inch Current Electricity:
b. Ohm circular per foot c. Ohm – meter
d. Ohm – centimeter Answer: c
Ques 7. The temperature coefficient of resistance of conductors is a. Positive
b. Zero c. Negative d. Infinite Answer: a
Ques 8. The temperature coefficient of resistance of semi‐conductors is a. Positive
b. Zero c. Negative d. Infinite Answer: c
Ques 9. One commercial unit of energy equals a. 500 watts – seconds
b. One‐watt hour c. One Kilo watt hour d. Ten Kilo watt hour Answer: c
Ques 10. In gases flow of current is due to a. Electrons only
b. Positive Ions only c. Electrons & Positive ions
d. Electrons, Positive ions and negative ions Answer: d
Ques 11. A 200 w lamp working for 24 hours will consume approximately…………units a. 50
b. 5 c. 24 d. 0.5 Answer: b
Ques 12. A positive charged body has a. Deficit of electrons b. Excess of neutrons c. Excess of electrons d. Deficit of protons Answer: a
Ques 13. A negative charged body has a. Deficit of electrons b. Excess of neutrons c. Excess of electrons d. Deficit of protons Answer: c
Ques 14. The maximum current rating for a 10 kΩ, 0.5W resistor is a. 0.707 mA
b. 7.07 mA c. 14.14 mA d. 28.28 mA Answer: b
Ques 15. An electrical lamp consumes 100W power. If the supply voltage is 220V, the energy consumed in 30 minutes is
a. 0.005 kWh b. 0.05 kWh c. 0.5 kWh d. 5 kWh Answer: b
Ques 16. Out of the following which is an insulating material a. Copper
b. Gold c. Silver d. Paper Answer: d
Ques 17. The property of a conductor due to which it passes current is called a. Resistance
b. Reluctance c. Conductance
d. Inductance Answer: c
Ques 18. Conductance is reciprocal of a. Resistance
b. Inductance c. Reluctance d. Capacitance Answer: a
Ques 19. The resistance of a conductor varies inversely as a. Length
b. Area of cross section c. Temperature
d. Resistivity Answer: b
Ques 20. With rise in temperature the resistance of pure metals a. Increases
b. Decreases
c. First increases then decreases d. Remains constant
Answer: a
Ques 21. When the temperature of copper wire is increased its resistance is a. Increased
b. Decreased c. Constant d. Zero Answer: a
Ques 22. An instrument which detects electric current is known as a. Voltmeter
b. Rheostat c. Wattmeter d. Galvanometer Answer: d
Ques 23. In a circuit, a 33Ω resistor carries a current of 2A. The voltage across the resistor is a. 33v
b. 66v c. 80v d. 132v Answer: b
Ques 24. Two resistors are said to be connected in series when a. Same current passes in turns through both b. Both carry the same value of current
c. Total current equals the sum of branch currents d. Sum of IR drops equals the applied EMF
Answer: a
Ques 25. Ohm’s law is not applicable to a. Vacuum tubes
b. Carbon resistors c. High voltage circuits
d. Circuit with low current densities Answer: a
Ques 26. Whenever a conductor cuts magnetic flux, an EMF is induced in it. This is known as a. Coulomb’s law
b. Joule’s law c. Faraday’s law d. Ohm’s law Answer: c
Ques 27. A law that states that the polarity of induced voltage will oppose the change in magnetic flux causing the induction
a. Joule’s law b. Faraday’s law c. Coulomb’s law d. Lenz’s law Answer: d
Ques 28. The net electrical charge in an isolated system remains constant. This is known as a. Law of conservation of charge
b. Coulomb’s first law c. Coulomb’s 2nd law
d. Law of conservation of energy
Answer: a
Ques 29. Varistors are a. Insulators
b. Nonlinear resistors c. Carbon resistors
d. Resistors with zero temperature co‐efficient Answer: b
Ques 30. Insulating materials have the function of
a. Preventing a short circuit between conducting wire
b. Preventing an open circuit between the voltage source and the load c. Conducting very large currents
d. Storing very high currents Answer: a
Ques 31. The rating of a fuse wire is always expressed in a. Ampere‐hours
b. Ampere‐volts c. kWh
d. Amperes Answer: d
Ques 32. The filament of an electrical bulb is made of a. Carbon
b. Aluminum c. Tungsten d. Nickle Answer: c
Ques 33. A 3Ω resistor having 2A current will dissipate the power of a. 2 watts
b. 4 watts c. 6 watts d. 8 watts Answer: c
Ques 34. Which of the following statement is true?
a. A galvanometer with low resistance in parallel is a voltmeter b. A galvanometer with high resistance in parallel is a voltmeter
c. A galvanometer with low resistance in series is an ammeter d. A galvanometer with high resistance in series is an ammeter Answer: c
Ques 35. If a parallel circuit is opened in the main line, the current a. Increases in the branch of the lowest resistance b. Increases in each branch
c. Is zero in all branches
d. Is zero in the highest resistance branch Answer: c
Ques 36. If one resistance in a series connection opens, then a. The current is zero in all other resistances b. The current is maximum in all other resistances c. The voltage is zero across the open resistance d. The voltage is infinite across the open resistance Answer: a
Ques 37. When resistances are connected in parallel, the total resistance is a. Less than the smallest resistance in the connection b. Greater than the smallest resistance in the connection
c. Between the smallest and greatest resistance in the connection d. Increasing and decreasing depending on the supply voltage Answer: a
Ques 38. Which factor does not affect resistance?
a. Length b. Resistivity
c. Cross sectional area d. Mass
Answer: d
Ques 39. Three 60W bulbs are in parallel across the 60V power line. If one bulb burns open a. There will be heavy current in the main line
b. Rest of the two bulbs will not light c. All three bulbs will light
d. The other two bulbs will light Answer: d
Ques 40. The four bulbs of 40W each are connected in series with a battery across them, which of the following statement is true
a. The current through each bulb is same b. The voltage across each bulb is not same c. The power dissipation in each bulb is not same d. None of the above
Answer: a
Ques 41. Heat in a conductor is produced on the passage of electric current is due to a. Reactance
b. Capacitance c. Impedance d. Resistance Answer: d
Ques 42. The insulation on a current carrying conductor is provided a. To prevent leakage of current
b. To prevent shock c. Both of above d. None of the above Answer: c
Ques 43. The thickness of insulation provided on the conductor depends on a. The magnitude of voltage on the conductor
b. The magnitude of current through the conductor c. Both of above
d. None of the above Answer: a
Ques 44. Which of the following quantities remain the same in all parts of a series circuit a. Voltage
b. Current c. Power d. Resistance Answer: b
Ques 45. A 40W bulb is connected in series with a room heater. If now 40W bulb is replaced by 100W bulb, the heater output will
a. Decrease b. Increase
c. Remain same d. Heater will burn Answer: b
Ques 46. Electric current passing through the circuit produces a. Magnetic effect
b. Luminous effect c. Thermal effect d. Chemical effect e. All of the above Answer: e
Ques 47. Resistance of material always decreases if a. Temperature of material is decreased b. Temperature of material is increased c. Number of free electrons becomes more d. None of the above
Answer: c
Ques 48. When electric current passes through a conductor, its temperature rises. This is due to a. Collision between conduction electrons and atoms
b. The release of conduction electrons from parent atoms c. Mutual collision between metal atoms
d. Mutual collision between conducting electrons Answer: a
Ques 49. Two bulbs of 500W and 200W rated at 250V will have resistance ratios as a. 4:25
b. 25:4 c. 2:5 d. 5:2 Answer: c
Ques 50. A glass rod when rubbed with silk cloth is charged because a. It takes in proton
b. Its atoms are removed c. It gives away electrons d. It gives away positive charge Answer: c
Ques 51. Two lamps 100W and 40W are connected in series across 230V AC. Which of the following statement is correct?
a. 100W lamp will glow brighter b. 40W lamp will glow brighter c. Both lamps will glow equally bright d. 40W lamp will fuse
Answer: b
Ques 52. When electric current passes through a bucket full of water, lots of bubbling appears. This suggests that the type of supply is
a. AC b. DC
c. Any of above d. None of the above Answer: b
Ques 53. Bulbs in street lighting are all connected in a. Parallel
b. Series
c. Series‐parallel d. End to end Answer: a
Ques 54. Sparking occurs when a load is switched off because the circuit has high a. Resistance
b. Inductance c. Capacitance d. Impedance Answer: b
Ques 55. Copper wire of certain lengths and resistance is drawn out to 3 times its length without change in volume. The new resistance of wire becomes
a. 1/9 times b. 3 times c. 9 times d. Unchanged.
Answer: c
Ques 56. Three identical resistors are first connected in parallel and then in series. The resultant resistance of the first combination to the second will be
a. 9 times b. 1/9 times c. 1/3 times d. 3 times Answer: b
Ques 57. Three 6 ohm resistors are connected to form a triangle. What is the resistance between any two corners?
a. 3/2 Ohm b. 6 Ohm c. 4 Ohm d. 8/3 Ohm Answer: c
Ques 58. Ohm’s law is not applicable to a. Semi‐conductors b. DC circuits c. Small resistors d. High currents Answer: a
Ques 59. Two copper conductors have equal lengths. The cross sectional area 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 the other conductor is
a. 160 Ohms b. 80 Ohms c. 20 Ohms d. 10 Ohms Answer: d
Ques 60. When current flows through heater coil, it glows. But the supply wire doesn’t glow. Why?
a. Current through supply line flows at lower speed.
b. Supply wire is covered with insulation layer c. Resistance of heater is more than the supply wire d. Supply wire is made of superior metal
Answer: c
Ques 61. An open resistor when checked with an Ohm‐meter reads a. Zero
b. Infinite
c. High but within tolerance d. Low but not zero
Answer: b
Ques 62. All good conductors have high a. Conductance
b. Resistance c. Reluctance
d. Thermal conductivity Answer: a
Ques 63. A thermistor has
a. Positive temperature coefficient b. Negative temperature coefficient c. Zero temperature coefficient d. Variable temperature coefficient Answer: b
Ques 64. Conductance : mho ::
a. Resistance : ohm b. Capacitance : Henry c. Inductance : farad d. Lumen : Steradian Answer: a
Ques 65. 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
Answer: d
Ques 66. The property of a conductor due to which it passes current is called (a) resistance
(b) reluctance (c) conductance (d) inductance
Answer: c
Ques 67. With rise in temperature the resistance of pure metals (a) increases
(b) decreases
(c) first increases and then decreases (d) remains constant
Answer: a
Ques 68. With rise in temperature the resistance of semi‐conductors (a) decreases
(b) increases
(c) first increases and then decreases (d) remains constant
Answer: a
Ques 69. An instrument which detects electric current is known as (a) voltmeter
(b) rheostat (c) wattmeter (d) galvanometer
Answer: d
Ques 70. You have to replace 1500 Q resistor in radio. You have no 1500 Q resistor but have several 1000 Q ones which you would connect
(a) two in parallel
(b) two in parallel and one in series (c) three in parallel
(d) three in series
Answer: b
Ques 71. Two resistors are said to be connected in series when (a) same current passes in turn through both
(b) both carry the same value of current
(c) total current equals the sum of branch currents (d) sum of IR drops equals the applied e.m.f.
Answer: a
Ques 72. Which of the following statement is true both for a series and a parallel D.C. circuit?
(a) Elements have individual currents (b) Currents are additive
(c) Voltages are additive (d) Power are additive
Answer: d
Ques 73. Which is the best conductor of electricity ? (a) Iron
(b) Silver (c) Copper (d) Carbon
Answer: a
Ques 74. The minimum charge on an ion is
(a) equal to the atomic number of the atom (b) equal to the charge of an electron
(c) equal to the charge of the number of electrons in an atom (#) zero
Answer: b
Ques 75. In a series circuit with unequal resistances
(a) the highest resistance has the most of the current through it (b) the lowest resistance has the highest voltage drop
(c) the lowest resistance has the highest current (d) the highest resistance has the highest voltage drop
Answer: d
Ques 76. If a wire conductor of 0.2 ohm resistance is doubled in length, its resistance becomes (a) 0.4 ohm
(b) 0.6 ohm (c) 0.8 ohm (d) 1.0 ohm
Answer: a
Ques 77. A 40 W bulb is connected in series with a room heater. If now 40 W bulb is replaced by 100 W bulb, the heater output will
(a) decrease (b) increase (c) remain same (d) heater will burn out
Answer: d
Ques 78. In an electric kettle water boils in 10 m minutes. It is required to boil the boiler in 15 minutes, using same supply mains
(a) length of heating element should be decreased (b) length of heating element should be increased
(c) length of heating element has no effect on heating if water (d) none of the above
Answer: a
Ques 79. An electric filament bulb can be worked from (a) D.C. supply only
(b) A.C. supply only (c) Battery supply only (d) All above
Answer: d
Ques 80. If the efficiency of a machine is to be high, what should be low ? (a) Input power
(b) Losses
(c) True component of power (d) kWh consumed
(e) Ratio of output to input
Answer: b
Ques 81. When electric current passes through a metallic conductor, its temperature rises. This is due to (a) collisions between conduction electrons and atoms
(b) the release of conduction electrons from parent atoms (c) mutual collisions between metal atoms
(d) mutual collisions between conducting electrons
Answer: a
Ques 82. Two bulbs of 500 W and 200 W rated at 250 V will have resistance ratio as (a) 4 : 25
(b) 25 : 4 (c) 2 : 5 (d) 5 : 2
Answer: c
Ques 83. Whether circuit may be AC. or D.C. one, following is most effective in reducing the magnitude of the current.
(a) Reactor (b) Capacitor (c) Inductor (d) Resistor
Answer: d
Ques 84. Two lamps 100 W and 40 W are connected in series across 230 V (alternating).
Which of the following statement is correct ? (a) 100 W lamp will glow brighter
(b) 40 W lamp will glow brighter (c) Both lamps will glow equally bright (d) 40 W lamp will fuse
Answer: b
Ques 85. In the case of direct current
(a) magnitude and direction of current remains constant (b) magnitude and direction of current changes with time (c) magnitude of current changes with time
(d) magnitude of current remains constant
Answer: b
Ques 86. When electric current passes through a bucket full of water, lot of bubbling is observed. This suggests that the type of supply is
(a) A.C.
(b) D.C.
(c) any of above two (d) none of the above
Answer: b
Ques 87. 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
Answer: d
Ques 88. Ohm’s law is not applicable to (a) semi‐conductors
(b) D.C. circuits (c) small resistors (d) high currents
Answer: a
Ques 89. 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
Answer: a
Ques 90. 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
Answer: b
Ques 91. A thermistor has
(a) positive temperature coefficient (b) negative temperature coefficient (c) zero temperature coefficient (d) variable temperature coefficient
Answer: c
Ques 92. For maximum transfer of power, internal resistance of the source should be (a) equal to load resistance
(b) less than the load resistance (c) greater than the load resistance (d) none of the above
Answer: a
Ques 93. The circuit has resistors, capacitors and semi‐conductor diodes. The circuit will be known as (a) non‐linear circuit
(b) linear circuit (c) bilateral circuit (d) none of the above
Answer: a
Ques 94. Application of Norton’s theorem to a circuit yields (a) equivalent current source and impedance in series (6) equivalent current source and impedance in parallel (c) equivalent impedance
(d) equivalent current source
Answer: a
Ques 95. Choose the incorrect statement.
(a) A branch formed by the parallel connection of any resistor R and open circuit has the characteristic of an open circuit.
(b) A branch formed by the parallel connection of any resistor R and a short circuit has the characteristic of a short circuit.
(c) A branch formed by the series connection of any resistor R and an open circuit has the characteristic of an open circuit.
(d) A branch formed by the series connection of any resistor R and a short circuit has the characteristic of resistor R.
Answer: a
Ques 1. The charge in the capacitor is stored at the a. Terminals
b. Plates c. Dielectric d. Air Answer: b
Ques 2. A capacitor is basically constructed of
a. Two conductors separated by a dielectric b. Two dielectric separated by a conductor c. Conductors and dielectric
d. Conductors and semi‐conductors Answer: a
Ques 3. Which component opposes voltage change?
a. Resistor b. Inductor c. Capacitor d. Transistor Answer: c
Ques 4. Which of the following describes the action of a capacitor?
a. Stores electrical energy
b. Opposes changes in current flow c. Creates a de‐resistance
d. Converts ac to dc Answer: a
Ques 5. For parallel capacitors, total charge is a. The sum of individual charges Capacitors:
b. Equal to the charge of either capacitors c. Equal to the product of the charges d. The quotient of the charges
Answer: a
Ques 6. A capacitor is used to a. Block the current b. Pass the current c. Open voltage source d. Short the voltage source Answer: a
Ques 7. The distance between the capacitor plates increases two times, then its capacitance a. Increases two times
b. Increases 4 times c. Decreases 2 times d. Decreases 4 times Answer: c
Ques 8. The area of capacitor plates increases two times, then its capacitance a. Increases two times
b. Increases 4 times c. Decreases 2 times d. Decreases 4 times Answer: a
Ques 9. 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
Answer: b
Ques 10. The lines of force due to charged particles are (a) always straight
(b) always curved (c) sometimes curved
(d) none of the above
Answer: b
Ques 11. 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
Answer: a
Ques 12. 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
Answer: b
Ques 13. Which of the following does not generally affect the value of a capacitor?
a. The dielectric material used b. The surface area of the plates c. The thickness of the dielectric d. The voltage applied to the plate Answer: d
Ques 14. If voltage across the plates of 2F capacitor is increased by 4V, then charge on the plates will a. Decreases by 2C
b. Increases by 2C c. Decreases by 4C d. Increases by 4C Answer: d
Ques 15. What does a capacitor store?
a. Voltage b. Charge c. Circuit d. Power
Answer: b
Ques 16. 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
Answer: b
Ques 17. 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
Answer: a
Ques 18. If three 10 uF capacitors are connected in parallel, the net capacitance is (a) 20 uF
(b) 30 uE (c) 40 uF (d) 50 uF
Answer: b
Ques 19. An electrolytic capacitor can be used for (a) D.C. only
(b) AC. only
(c) both D.C. as well as A.C.
Answer: a
Ques 20. If A.C. voltage is applied to capacitive circuit, the alternating current can flow in the circuit because (a) varying voltage produces the charging and dicharging currents
(b) of high peak value (c) charging current can flow (d) discharge current can flow
Answer: a
Ques 21. Which of the following statements is correct ?
(a) Air capacitors have a black band to indicate the outside foil (6) Electrolytic capacitor must be connected in the correct polarity (c) Ceramic capacitors must be connected in the correct polarity (d) Mica capacitors are available in capacitance value of 1 to 10 pF
Answer: b
Ques 22. “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
Answer: b
Ques 23. 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
Answer: c
Ques 1. When capacitors are connected in parallel, the total capacitance is a. Greater than the largest capacitor
b. Smaller than the largest capacitor c. Smaller than the smallest capacitor d. Greater than the smallest capacitor Answer: a
Ques 24. 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
Answer: b
Ques 25. In a capacitor the electric charge is stored in (a) metal plates
(b) dielectric (c) both (a) and (6) (d) none of the above
Answer: b
Ques 26. Which of the following statements is incorrect ?
(a) The leakage resistance of ceramic capacitors is generally high
(b) The stored energy in a capacitor decreases with reduction in value of capacitance (c) The stored energy in a capacitor increases with applied voltage
(d) A wire cable has distributed capacitance between the conductors
Answer: b
Ques 27. The sparking between two electrical contacts can be reduced by inserting a (a) capacitor in parallel with contacts
(6) capacitor in series with each contact (c) resistance in line
(d) none of the above
Answer: a
Ques 28. The power dissipated in a pure capacitor is (a) zero
(6) proportional to applied voltage (c) proportional to value of capacitance (d) both (b) and (c) above
Answer: a
Ques 29. In a capacitive circuit
(a) a steady value of applied voltage causes discharge (b) an increase in applied voltage makes a capacitor charge (c) decrease in applied voltage makes a capacitor charge (d) none of the above
Answer: b
Ques 30. Capacitance increases with
(a) increase in plate area and decrease in distance between the plates (b) increase in plate area and distance between the plates
(c) decrease in plate area and value of applied voltage (d) reduction in plate area and distance between the plates
Answer: a
Ques 31. A capacitor consists of
(a) two insulators separated by a conductor (b) two conductors separated by an insulator (c) two insulators only
(d) two conductors only
Answer: b
Ques 32. A capacitor in a circuit became hot and ultimately exploded due to wrong connections, which type of capacitor it could be ?
(a) Paper capacitor (b) Ceramic capacitor (c) Electrolytic capacitor (d) Any‐of the above
Answer: c
Ques 33. Energy stored in the electric field of a capacitor C when charged from a D.C source of voltage V is equal to joules
(a) CV2 (b) C2V (c) CV2 (d) CV Answer: a
Ques 34. When 4 volts e.m.f. is applied across a 1 farad capacitor, it will store energy of (a) 2 joules
(b) 4 joules (c) 6 joules
(d) 8 joules
Answer: d
Ques 35. The capacitor preferred for high frequency circuits is (a) air capacitor
(b) mica capacitor (c) electrolytic capacitor (d) none of the above
Answer: b
Ques 36. While testing a capacitor with ohm meter, if the capacitor shows charging, but the final resistance reading is appreciably less than normal, it can be concluded that the capacitor is
(a) short‐circuited (b) open circuited (c) alright
(d) leaky
Answer: d
Ques 37. Which of the following capacitors will have the least value of breakdown voltage ? (a) Mica
(b) Paper (c) Ceramic (d) Electrolytic
Answer: d
Ques 38. The value of dielectric constant for vacuum is taken as (a) zero
(b) 1 (c) 4 (d) 10 Answer: b
Ques 39. Which of the following statements is incorrect ?
(a) The thinner the dielectric, the more the capacitance and the lower the voltage breakdown rating for a capacitor .
(b) A six dot mica capacitor colour coded white, green, black, red and yellow has the capacitance value of 500 pF
(c) Capacitors in series provide less capacitance but a higher voltage breakdown rating for the combination
(d) A capacitor can store charge because it has a dielectric between two conductors
Answer: b
Ques 40. Capacitors are mainly used for radio frequency tuning.
(a) Paper (b) Air (c) Mica (d) Electrolytic
Answer: b
Ques 41. Capacitors are used in transistor circuits.
(a) Ceramic (b) Paper (c) Air
(d) Electrolytic
Answer: a
Ques 1. The process by which an EMF and hence current is generated in a conductor when there is a change in the magnetic flux linking the conductor is called?
a. Electromagnetic induction b. Mutual induction
c. Faraday’s law
d. Electromagnetic interference Answer: a
Ques 2. The property of coil by which a counter EMF is induced in it when the current through the coil changes is known as
a. Self‐Inductance Electromagnetic Induction
b. Mutual Inductance c. Series aiding inductance d. Capacitance
Answer: a
Ques 3. The EMF induced in a coil due to the changing current of another neighboring coil is called a. Mutually induced EMF
b. Self‐induced EMF c. Statically induced EMF d. Dynamically induced EMF Answer: a
Ques 4. As per Faraday’s laws of electromagnetic induction and EMF is induced in a conductor whenever it a. Lies perpendicular to the magnetic field
b. Lies in a magnetic field c. Cuts magnetic flux
d. Moves parallel to the direction of the magnetic field Answer: c
Ques 5. If current in a conductor increases then according to Lenz’s law, self‐induced voltage will a. Aid the increasing current
b. Tend to decrease the amount of current
c. Produce current opposite to the increasing current d. Aid the applied voltage
Answer: c
Ques 6. The direction of Induced EMF can be found by a. Laplace’s law
b. Lenz’s law
c. Fleming’s right hand rule d. Kirchhoff’s law
Answer: b
Ques 7. The magnitude of the induced EMF in a conductor depends on the a. Flux density of the magnetic field
b. Amount of flux cut c. Amount of flux linkages d. Rate of change of flux linkages Answer: d
Ques 8. Which of the following is unit of inductance?
a. Ohm b. Henry
c. Ampere turns d. Weber / meter Answer: b
Ques 9. A coil with negligible resistance has 50V across it with 10 mA. The inductive reactance is a. 50 ohms
b. 500 ohm c. 1000 ohm d. 5000 ohm Answer: d
Ques 10. Lenz’s law is a consequence of the law of conservation of a. Induced current
b. Charge c. Energy d. Induced EMF Answer: c
Ques 11. Which circuit element will oppose the change in circuit current?
a. Resistance only b. Inductance only c. Capacitance only
d. Inductance and capacitance Answer: b
Ques 12. The phenomenon of an uncharged body getting charged merely by the nearness of a charged body is known as
(a) pholoelectric effect (b) chemical effect (c) magnetic effect (d) induction
Answer: d
Ques 1. 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
Answer: a
Ques 2. During charging the specific gravity of the electrolyte of a lead‐acid battery (a) increases
(b) decreases
(c) remains the same (d) becomes zero
Answer: a
Ques 3. The best indication about the state of charge on a lead‐acid battery is given by (a) output voltage
(b) temperature of electrolyte (c) specific gravity of electrolyte (d) none of the above
Answer: c
Ques 4. The output voltage of a charger is (a) less than the battery voltage (b) higher than the battery voltage (c) the same as the battery voltage (d) none of the above
Answer: b
Ques 5. As compared to constant‐current system, the constant‐voltage system of charging a lead acid cell has the advantage of
(a) reducing time of charging Electrolysis and Storage of Batteries
(b) increasing cell capacity (c) both (a) and (b)
(d) avoiding excessive gassing
Answer: c
Ques 6. A dead storage battery can be revived by (a) adding distilled water
(6) adding so‐called battery restorer (c) a dose of H2SO4
(d) none of the above
Answer: d
Ques 7. Trickle charging of a storage battery helps to (a) maintain proper electrolyte level
(b) increase its reserve capacity (c) prevent sulphation
(d) keep it fresh and fully charged
Answer: d
Ques 8. In a lead‐acid cell dilute sulfuric acid (electrolyte) approximately comprises the following (a) one part H2O, three parts H2SO4
(b) two parts H2O, two parts H2SO4 (c) three parts H2O, one part H2SO4 (d) all H2S04
Answer: c
Ques 9. The ampere‐hour efficiency of a leadacid cell is normally between (a) 20 to 30%
(b) 40 to 50%
(c) 60 to 70%
(d) 90 to 95%
Answer: d
Ques 10. The average charging voltage for alkali cell is about (a) 1 V
(b) 1.2 V (c) 1.7 V (d) 2.1 V
Answer: c
Ques 11. Lead‐acid cell has a life of nearly charges and discharges (a) 500
(b) 700 (c) 1000 (d) 1250
Answer: d
Ques 12. The internal resistance of a lead‐acid cell is that of Edison cell (a) less than
(b) more than (c) equal to
(d) none of the above
Answer: a
Ques 13. Electrolyte used in a lead‐acid cell is (a) NaOH
(b) onlyH2S04 (c) only water (d) dilute H2SO4
Answer: d
Ques 14. The specific gravity of electrolyte is measured by (a) manometer
(6) a mechanical gauge (c) hydrometer
(d) psychrometer
Answer: c
Ques 15. When the specific gravity of the electrolyte of a lead‐acid cell is reduced to 1.1 to 1.15 the cell is in (a) charged state
(b) discharged state (c) both (a) and (b) (d) active state
Answer: b
Ques 16. Over charging
(a) produces excessive gassing (b) loosens the active material
(e) increases the temperature resulting in buckling of plates (d) all above
Answer: d
Ques 17. Undercharging
(a) reduces specific gravity of the electrolyte (b) increases specific gravity of the electrolyte (c) produces excessive gassing
(d) increases the temperature
Answer: a
Ques 18. Internal short circuits are caused by (a) breakdown of one or more separators
(b) excess accumulation of sediment at the bottom of the cell (c) both (a) and (b)
(d) none of the above
Answer: c
Ques 19. On overcharging a battery
(a) it will bring about chemical change in active materials (b) it will increase the capacity of the battery
(c) it will raise the specific gravity of the electrolyte (d) none of the above will occur
Answer: d
Ques 20. Each cell has a vent cap
(a) to allow gases out when the cell is on charge (b) to add water to the cell if needed
(c) to check the level of electrolyte (d) to do all above functions
Answer: d
Ques 21. Following will occur if level of electrolyte falls below plates (a) capacity of the cell is reduced
(b) life of the cell is reduced
(c) open plates are converted to lead sulphate (d) all above
Answer: d
Ques 22. 48 ampere‐hour capacity would deliver a current of (a) 48 amperes for 1 hour
(b) 24 amperes for 2 hours (c) 8 amperes for 6 hours (d) 6 amperes for 8 hours
Answer: d
Ques 23. A 12V battery is rated at 48 AH. If it must deliver an average of 2 A, how long will the battery last before it needs recharging?
a. 48 Hours b. 4 Hours c. 96 Hours d. 24 Hours Answer: d
Ques 24. To increase the voltage output, cells are connected in a. Parallel
b. Series parallel c. Parallel series d. Series
Answer: d
Ques 25. Connecting batteries of equal voltage in parallel
a. Multiplies the voltage available b. Increases the internal resistance c. Reduces the power available d. Multiplies the current available Answer: d
Ques 26. In constant‐current charging method, the supply voltage from discharged to fully charged condition
(a) decreases (b) increases
(c) remains constant (d) none of the above
Answer: b
Ques 27. In constant voltage charging method, the charging current from discharged to fully charged condition
(a) decreases (b) increases
(c) remains constant (d) none of the above
Answer: a
Ques 28. Battery charging equipment is generally installed (a) in well ventilated location
(b) in clean and dry place
(c) as near as practical to the battery being charged (d) in location having all above features
Answer: d
Ques 29. Following will happen if the specific gravity of electrolyte becomes more than 1.23.
(a) Loss of capacity (b) Loss of life
(c) Corrosion of the grids of the plate (d) All above
Answer: d
Ques 30. Cell short circuit results in (a) low sp. gravity electrolyte (b) abnormal high temperature (c) reduced gassing on charge (d) all above
Answer: d
Ques 31. Internal resistance of a cell is reduced by
(a) using vent plug to permit gas formed during discharge (b) increasing the plate area
(c) putting plates very close together (d) all above methods
Answer: d
Ques 32. Capacity of dry cells is
(a) more when it is supplying current for intermittent periods (b) more when it is supplying current for continuous periods (c) unaffected by the type of discharge
(d) none of the above
Answer: a
Ques 33. In a lead‐acid cell, if the specific gravity of sulphuric acid is 1.8, it will require following ratio of acid to water to get mixture of specific gravity of 1.3
(a) 6 parts of acid to 4 parts of water (b) 4 parts of acid to 4 parts of water (c) 4 parts of acid to 6 parts of water (d) 4 parts of acid to 8 parts of water
Answer: c
Ques 34. Following will happen if battery charging rate is too high (a) excessive gassing will occur
(b) temperature rise will occur
(c) bulging and buckling of plates will occur (d) all above will occur
Answer: d
Ques 35. What refers to a method in which the charger and the battery are always connected to each other for supplying current to the load?
a. Continuous charging b. Float charging c. Infinite charging d. On line charging Answer: b
Ques 36. If a battery is wrongly connected on charge following will happen (a) current delivered by the battery will be high
(b) current drawing will be nil (c) current drawing will be very small (d) current drawing will be very high
Answer: d
Ques 37. _____ of electrolyte indicates the state of charge of the battery (a) colour
(b) mass (c) viscosity (d) specific gravity
Answer: d
Ques 38. The following indicate that battery on charge has attained full charge (a) colour of electrode
(b) gassing (c) specific gravity (d) all above
Answer: d
Ques 39. Capacity of a battery.is expressed in (a) Ah
(b) Vh (c) Wh (d) kWh
Answer: a
Ques 40. A battery of 6 cells will show a drop of _____ volts from fully charged state to fully discharged state.
(a) 1.0 (b) 1.5 (c) 2.4 (d) 2.9 Answer: c
Ques 41. Hydrogen evolved during charging produces explosive mixture when it is more than (a) 2%
(b) 4%
(c) 6%
(d) 8%
Answer: d
Ques 42. While preparing electrolyte for a lead‐acid battery (a) water is poured into acid
(b) acid is poured into water
(c) anyone of the two can be added to other chemical
Answer: b
Ques 43. Which of the following is incorrect ?
(a) A storage cell has a reversible chemical reaction (b) A lead‐acid cell can be recharged
(c) A carbon‐zinc cell has unlimited shelf life
(d) A primary cell has an irreversible chemical reaction
Answer: c
Ques 44. When two batteries are connected in parallel, it should be ensured that (a) they have same e.m.f.
(b) they have same make
(c) they have same ampere‐hour capacity (d) they have identical internal resistance
Answer: a
Ques 45. Petroleum jelly is applied to the electrical connections to the lead‐acid battery (a) prevent local heating
(b) prevent short‐circuiting (c) reduce path resistance (d) prevent corrosion
Answer: d
Ques 46. Which of the following factors adversely affects the capacity of the lead acid battery?
(a) Temperature of surroundings (b) Specific gravity of electrolyte (c) Rate of discharge
(d) All of the above
Answer: d
Ques 1. 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
Answer: d
Ques 2. The concept on which Superposition theorem is based is (a) reciprocity
(b) duality (c) non‐linearity (d) linearity
Answer: d
Principle of AC and DC Current:
Ques 3. To determine the polarity of the voltage drop across a resistor, it is necessary to know (a) value of current through the resistor
(b) direction of current through the resistor (c) value of resistor
(d) e.m.fs. in the circuit
Answer: b
Ques 4. “Maximum power output is obtained from a network when the load resistance is equal to the output resistance of the network as seen from the terminals of the load”. The above statement is associated with
(a) Millman’s theorem (b) Thevenin’s theorem (c) Superposition theorem
(d) Maximum power transfer theorem
Answer: d
Ques 5. A star circuit has element of resistance R/2. The equivalent delta elements will be (a) R/6
(b) fi?
(c) 2R (d) 4R Answer: b
Ques 6. The time constant of an R‐C circuit is defined as the time during which capacitor charging voltage actually rises to ______ percent of its value.
(a) 37, initial (b) 62, initial (c) 62, final (d) 37, final
Answer: c
Ques 7. What will happen to an insulating medium if voltage more than the breakdown voltage is applied on it ?
(a) It will become magnetic (b) It will melt
(c) It will get punctured or cracked
(d) Its molecular structure will get changed
Answer: c
Ques 8. The bridge used for the measurement of the value of the capacitance is (a) Wien’s bridge
(b) Wheatstone bridge (c) Schering bridge (d) Hay’s bridge
Answer: c
Ques 9. An uncharged conductor is placed near a charged conductor, then (a) the uncharged conductor gets charged by conduction
(6) the uncharged conductor gets charged by induction and then attracted towards the charging body
(c) the uncharged conductor is attracted first and then charged by induction (d) it remains as such
Answer: b
Ques 10. 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 Answer: c
Ques 11. The form factor is the ratio of (a) peak value to r.m.s. value (6) r.m.s. value to average value (c) average value to r.m.s. value (d) none of the above
Answer: b
Ques 12. 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
Answer: b
Ques 13. The voltage of domestic supply is 220V. This figure represents (a) mean value
(b) r.m.s. value (c) peak value (d) average value
Answer: a
Ques 14. 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°
Answer: b
Ques 15. The r.m.s. value and mean value is the same in the case of (a) triangular wave
(6) sine wave (c) square wave
(d) half wave rectified sine wave
Answer: c
Ques 16. 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
Answer: a
Ques 17. 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
Answer: a
Ques 18. 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
Answer: b
Ques 19. The ratio between the active power and apparent power of a load in an AC circuit is called a. Quality factor
b. Power factor c. Power ratio d. Power reactive Answer: b
Ques 20. When the power factor of a circuit is zero a. Power absorbed is maximum b. Power absorbed is minimum c. Power absorbed is zero d. The impedance is minimum Answer: c
Ques 21. 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
Answer: e
Ques 22. 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 (6) will change the resonance frequency
(c) will change the impedance at resonance frequency (d) will increase the selectivity of the circuit
Answer: d
Ques 23. 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
Answer: c
Ques 24. 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)
Answer: e
Ques 25. 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
Answer: a
Ques 26. Power factor of the following circuit will be zero (a) resistance
(b) inductance (c) capacitance
(d) both (b) and (c)
Answer: d
Ques 27. Power factor of the following circuit will be unity (a) inductance
(b) capacitance (c) resistance (d) both (a) and (b)
Answer: c
Ques 28. 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
Answer: d
Ques 29. In a loss‐free R‐L‐C circuit the transient current is (a) oscillating
(b) square wave (c) sinusoidal (d) non‐oscillating
Answer: c
Ques 30. The double energy transient occur in the (a) purely inductive circuit
(b) R‐L circuit (c) R‐C circuit (d) R‐L‐C circuit
Answer: d
Ques 31. The power factor at resonance in R‐L‐ C parallel circuit is (a) zero
(b) 0.08 lagging (c) 0.8 leading
(d) unity
Answer: d
Ques 32. 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
Answer: d
Ques 33. 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°
Answer: b
Ques 34. 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
Answer: c
Ques 35. Inductance of coil
(a) is unaffected by the supply frequency
(b) decreases with the increase in supply frequency (c) increases with the increase in supply frequency (d) becomes zero with the increase in supply frequency
Answer: c
Ques 36. 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 the decrease of inductance and decrease of resistance
(d) increases with decrease of inductance and increase of resistance
Answer: a
Ques 37. Time constant of a capacitive circuit
(a) increases with the decrease of capacitance and decrease of resistance (b) increases with the decrease of capacitance and increase of resistance (c) increases with the increase of capacitance and decrease of resistance (d) increase with increase of capacitance and increase of resistance
Answer: d
Ques 38. Magnitude of current at resonance in R‐L‐C circuit (a) depends upon the magnitude of R
(b) depends upon the magnitude of L (c) depends upon the magnitude of C
(d) depends upon the magnitude of R, Land C
Answer: a
Ques 39. In a R‐L‐C circuit
(a) power is consumed in resistance and is equal to I R
(b) exchange of power takes place between inductor and supply line (c) exchange of power takes place between capacitor and supply line
(d) exchange of power does not take place between resistance and the supply line (e) all above are correct
Answer: e
Ques 40. Which of the following coil will have large resonant frequency ? (a) A coil with large resistance
(b) A coil with low resistance
(c) A coil with large distributed capacitance (d) A coil with low distributed capacitance
Answer: c
Ques 41. In an AC. circuit, a low value of kVAR compared with kW indicates (a) low efficiency
(b) high power factor
(c) unity power factor (d) maximum load current
Answer: b
Ques 42. All definitions of power factor of a series R‐L‐C circuit are correct except (a) ratio of net reactance and impedance
(b) ratio of kW and kVA (c) ratio of J and Z (d) ratio of W and VA
Answer: a
Ques 43. The apparent power drawn by an A.C. circuit is 10 kVA and active power is 8 kW. The reactive power in the circuit is
(a) 4 kVAR (b) 6 kVAR (c) 8 kVAR (d) 16 kVAR
Answer: b
Ques 44. What will be the phase angle between two alternating waves of equal frequency, when one wave attains maximum value the other is at zero value ?
(a) 0°
(b) 45°
(c) 90°
(d) 180°
Answer: c
Ques 45. In an A.C. circuit power is dissipated in (a) resistance only
(b) inductance only (c) capacitance only (d) none of the above
Answer: a
Ques 46. In a parallel R‐C circuit, the current always______the applied voltage (a) lags
(b) leads
(c) remains in phase with (d) none of the above
Answer: b
Ques 47. The power is measured in terms of decibles in case of (a) electronic equipment
(b) transformers
(c) current transformers (d) auto transformers
Answer: a
Ques 48. Capacitive susceptance is a measure of (a) reactive power in a circuit
(b) the extent of neutralisation of reactive power in a circuit (c) a purely capacitive circuit’s ability to pass current
(d) a purely capacitive circuit’s ability to resist the flow of current
Answer: c
Ques 49. A parallel AC. circuit in resonance will
(a) have a high voltage developed across each inductive and capacitive section (b) have a high impedance
(c) act like a resistor of low value
(d) have current in each section equal to the line current
Answer: b
Ques 50. The inductance of a coil can be increased by (a) increasing core length
(b) decreasing the number of turns (c) decreasing the diameter of the former
(d) choosing core material having high relative permeability
Answer: d
Ques 51. In a three‐phase supply floating neutral is undesirable because it way give rise to (a) high voltage across the load
(b) low voltage across the load
(c) unequal line voltages across the load
Answer: c
Ques 52. The r.m.s. value of half wave rectified sine wave is 200 V. The r.m.s. value of full wave rectified AC.
will be (a) 282.8 V (b) 141.4 V (c) 111 V (d) 100 V
Answer: a
Ques 53. The frequency of an alternating current is (a) the speed with which the alternator runs (b) the number of cycles generated in one minute
(c) the number of waves passing through a point in one second (d) the number of electrons passing through a point in one second
Answer: c
Ques 54. An A.C. voltage is impressed across a pure resistance of 3.5 ohms in parallel with a pure inductance of impedance of 3.5 ohms,
(a) the current through the resistance is more (b) the current through the resistance is less
(c) both resistance and inductance carry equal currents (d) none of the above
Answer: c
Ques 55. In a pure inductive circuit if the supply frequency is reduced to 1/2, the current will (a) be reduced by half
(b) be doubled
(c) be four times as high (d) be reduced to one fourth
Answer: b
Ques 56. In a pure capacitive circuit if the supply frequency is reduced to 1/2, the current will (a) be reduced by half
(b) be doubled
(c) be four times at high (d) be reduced to one fourth
Answer: a
Ques 57. In each of the three coils of a three phase generator, an alternating voltage having an r.m.s. value of 220 V is induced. Which of the following values is indicated by the voltmeters ?
(a) 220 V (b) 220V3V (c) 220/V3 V
(d) none of the above
Answer: a
Ques 1. According to Fleming’s right‐hand rule for finding the direction of induced e.m.f., when middle finger points in the direction of induced e.m.f., forefinger will point in the direction of
(a) motion of conductor (b) lines of force
(c) either of the above (d) none of the above
Answer: b
Ques 2. In D.C. generators, the cause of rapid brush wear may be (a) severe sparking
(b) rough commutator surface (c) imperfect contact
(d) any of the above
Answer: d
DC Generators and DC Motors:
Ques 3. For a D.C. generator when the number of poles and the number of armature conductors is fixed, then which winding will give the higher e.m.f. ?
(a) Lap winding (b) Wave winding
(c) Either of (a) and (b) above
(d) Depends on other features of design
Answer: b
Ques 4. In a four‐pole D.C. machine
(a) all the four poles are north poles (b) alternate poles are north and south (c) all the four poles are south poles (d) two north poles follow two south poles
Answer: b
Ques 5. In case of D.C. machines, mechanical losses are primary function of (a) current
(b) voltage (c) speed
(d) none of above
Answer: c
Ques 6. In D.C. generators, current to the external circuit from armature is given through (a) commutator
(b) solid connection (c) slip rings
(d) none of above
Answer: a
Ques 7. Brushes of D.C. machines are made of (a) carbon
(b) soft copper (c) hard copper (d) all of above
Answer: a
Ques 8. In case of a 4‐pole D.C. generator provided with a two layer lap winding with sixteen coils, the pole pitch will be
(a) 4 (b) 8 (c) 16 (d) 32 Answer: b
Ques 9. D.C. generators are connected to the busbars or disconnected from them only under the floating condition
(a) to avoid sudden loading of the primemover (b) to avoid mechanicaljerk to the shaft (c) to avoid burning of switch contacts (d) all above
Answer: d
Ques 10. Eddy currents are induced in the pole shoes of a D.C. machine due to (a) oscillating magnetic field
(b) pulsating magnetic flux
(c) relative rotation between field and armature (d) all above
Answer: c
Ques 11. The function of pole shoes in the case of D.C. machine is (a) to reduce the reluctance of the mag¬netic path (b) to spread out the flux to achieve uniform flux density (c) to support the field coil
(d) to discharge all the above functions
Answer: d
Ques 12. Which of the following statement about D.C. generators is false ? (a) Compensating winding in a D.C. machine helps in commutation
(b) In a D. C. generator interpoles winding is connected in series with the armature winding (c) Back pitch and front pitch are both odd and approximately equal to the pole pitch (d) Equilizing bus bars are used with parallel running of D.C. shunt gen¬erators
