Electrical Basic Questions 13
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1) In case of a synchronous generator, armature winding and field winding are
a. Both stationary
b. Stationary, rotating
c. Rotating, stationary
d. Both rotating
ANSWER: Stationary, rotating
2) Salient pole type motors have
a. Large diameter and large axial length
b. Small diameter and small axial length
c. Large diameter and small axial length
d. Small diameter and large axial length
ANSWER: Large diameter and small axial length
3) Short pitched windings are mainly used because it
a. Gives better waveform of the generated emf
b. Eddy current and hysteresis losses are reduced
c. Less copper is used
d. All of these
ANSWER: All of these
4) The number of conductors in synchronous generators is equal to
a. The number of turns per phase
b. Twice the number of coils per phase
c. Half of the number of coils per phase
d. None of these
ANSWER: Twice the number of coils per phase
5) If Kf, Kc and Kd are the coefficient of form factor, pitch factor and distribution factor respectively then the rms value of induced emf per phase is given by
a. KfKcKd f ∅T
b. 1.414KfKcKd f ∅T
c. 4KfKcKd f ∅T
d. 1.11KfKcKd f ∅T
ANSWER: 4KfKcKd f ∅T
Electrical Basic Questions 13
6) The steel used for laminations should have
a. High permeability and high hysteresis
b. High permeability and low hysteresis
c. Low permeability and hysteresis
d. Low permeability and high hysteresis
ANSWER: High permeability and low hysteresis
7) In core type transformer, the coils are wound in helical layers, each layers being insulated from each other by using
a. Paper
b. Cloth
c. Cooling ducts
d. All of these
ANSWER: All of these
8) In transformer if the secondary is open circuited then its terminal voltage is
a. Same as the induced emf
b. Greater than the induced emf
c. Lesser than the induced emf
d. None of these
ANSWER: Same as the induced emf
9) If ∅m is the maximum value of flux in the core then the average rate of change of flux is
a. f∅m
b. 2 f∅m
c. 4 f∅m
d. 4.44 f∅m
ANSWER: 4 f∅m
10) If R1 is the primary winding resistance and R2 is the secondary winding resistance then the equivalent resistance of the transformer as referred to the primary is
a. R1+ R2/K2
b. R2+ R1/K2
c. R1+ K2R2
d. R2+ K2R1
ANSWER: R1+ R2/K2
Electrical Basic Questions 13
11) For induction motors,
a. Should be essentially a constant speed motor
b. Its speed reduces to some extent with increase in load
c. Does not need to be synchronized
d. All of these
ANSWER: All of these
12) In induction motor, greater the number of poles
a. Lesser the speed
b. Greater the speed
c. Lesser the frequency
d. All of these
ANSWER: Lesser the speed
13) The advantage of skewing in induction motor is / are
a. Motor runs smoothly as the magnetic hum is reduced
b. The tendency of the rotor teeth to remain under the stator teeth due to direct magnetic attraction is reduced
c. More uniform torque is obtained while running
d. All of these
ANSWER: All of these
14) Slip ring induction motor are employed only for
a. Speed control
b. High starting torque
c. Both (a) and (b)
d. None of these
ANSWER: Both (a) and (b)
15) The resultant flux in an induction motor is equal to the
a. Maximum value of flux due to any phase
b. Twice of the maximum value of flux due to any phase
c. 0.5 times the maximum value of flux due to any phase
d. 1.5 times the maximum value of flux due to any phase
ANSWER: 1.5 times the maximum value of flux due to any phase
Electrical Basic Questions 13
16) Electrical energy can be converted into
a. Light energy
b. Electromagnetic energy
c. Electrochemical energy
d. All of these
ANSWER: All of these
17) In a gas filled lamp, inert gases are filled in the lamp to
a. Compensate heat losses
b. Minimize the electricity use
c. Increase the brightness
d. None of these
ANSWER: Compensate heat losses
18) If the length of the filament is increased then the
a. Power also increases
b. Power decreases
c. Required oxygen increases
d. Flow of current increases
ANSWER: Power also increases
19) The tube of a tube light is filled with
a. Fluorescent paste
b. Low pressure inert gas
c. Mercury
d. Only (b) and (c)
ANSWER: Only (b) and (c)
20) Electric bell consists of a
a. Horse shoe type electromagnet
b. Circular electromagnet
c. Rod shaped electromagnet
d. All of these
ANSWER: Horse shoe type electromagnet
Electrical Basic Questions 13
21) In cell, the current flows in outer circuit from
a. Positive terminal to negative terminal and electrons from negative terminal to positive terminal
b. Positive terminal to negative terminal and electrons from positive terminal to negative terminal
c. Negative terminal to positive terminal and electrons from negative terminal to positive terminal
d. Negative terminal to positive terminal and electrons from positive terminal to negative terminal
ANSWER: Positive terminal to negative terminal and electrons from negative terminal to positive terminal
22) Leclanche cell Daniel cell is an example of
a. both dry cell
b. both wet cell
c. dry cell, wet cell
d. wet cell, dry cell
ANSWER: both wet cell
23) Secondary’s cells are
a. lead acid cell
b. alkaline cell
c. both (a) and (b)
d. none of these
ANSWER: both (a) and (b)
24) In voltaic cell, anode and cathode of the cell is
a. copper electrode, zinc
b. zinc, copper
c. aluminium, zinc
d. nickel, cobalt
ANSWER: copper electrode, zinc
Electrical Basic Questions 13
25) In Daniel cell,
a. Layer of hydrogen bubbles is formed
b. Polarization takes place
c. Negative pole is a copper vessel
d. None of these
ANSWER: None of these
26) For controlling the initial inrush current,
a. Reduced voltage is applied to the stator during the starting period
b. Reduced voltage is applied to the stator when the motor is running at rated speed
c. Either (a) or (b)
d. None of these
ANSWER: Reduced voltage is applied to the stator during the starting period
27) In India, direct – on – line starter can be used for 3 – phase squirrel cage induction motor up to the rating of
a. 5 HP
b. 10 HP
c. 15 HP
d. 25 HP
ANSWER: 5 HP
28) Reduced voltage can be applied across the stator circuit by
a. Using an autotransformer
b. Connecting resistor in series with stator winding
c. Connecting inductor in series with stator winding
d. All of these
ANSWER: All of these
Electrical Basic Questions 13
29) If an induction motor is initially connected in delta and then reconnected instar then the current drawn will become
a. Thrice of the current drawn when connected in delta
b. Twice of the current drawn when connected in delta
c. One third of the current drawn when connected in delta
d. Half of the current drawn when connected in delta
ANSWER: One third of the current drawn when connected in delta
30) If an extra resistance is connected in the rotor circuit of slip ring induction motor, then
a. Starting current and torque decreases
b. Starting current increases and torque decreases
c. Starting current decreases and torque increases
d. Starting current and torque increases
ANSWER: Starting current decreases and torque increases
31) The atomic number of silicon and germanium is
a. 32, 14
b. 12, 19
c. 14, 32
d. 19, 12
ANSWER: 14, 32
32) To move electrons from valence band to conduction band, the energy applied to the insulator is
a. Less than 15 eV
b. Equal to 15 eV
c. More than 15 eV
d. More than 25 eV
ANSWER: More than 15 eV
Electrical Basic Questions 13
33) Valence electrons of silicon and germanium are
a. 2, 4
b. 4, 4
c. 4, 2
d. 2, 2
ANSWER: 4, 4
34) At low temperature, the semi conductor behaves as a
a. Perfect insulator
b. Perfect conductor
c. Perfect consulator
d. None of these
ANSWER: Perfect consulator
35) If an external electric field is applied across the intrinsic semiconductor, then the
a. More number of electron holes pair combination will be broken
b. More number of electron holes pair combination will be evolved
c. Less number of electron holes pair combination will be broken
d. Less number of electron holes pair combination will be evolved
ANSWER: More number of electron holes pair combination will be broken
Electrical Basic Questions 13
36) According to Kirchoff’s voltage law,
a. The algebraic sum of all the e.m.f’s in the circuit is zero
b. Algebraic sum all the voltage drops in the circuit is zero
c. Algebraic sum of e.m.f’s plus algebraic sum of voltage drops is equal to zero
d. All of these
ANSWER: Algebraic sum of e.m.f’s plus algebraic sum of voltage drops is equal to zero
37) Electrical work is
a. Directly proportional to the potential difference
b. Directly proportional to the charge
c. Directly proportional to the current
d. All of these
ANSWER: All of these
38) If a current of 5A flows through a resistor of 12 ohm then the power developed and the energy dissipated in 2 minutes are
a. 300 W, 36000 J
b. 360 W, 30000 J
c. 380 W, 35000 J
d. 380 W, 36000 J
ANSWER: 300 W, 36000 J
39) The unit of electrical energy is / are
a. Joules
b. Watt – sec
c. Kilowatt – hour
d. All of these
ANSWER: All of these
Electrical Basic Questions 13
40) If a number of resistors are connected in parallel, then the reciprocal of total resistance is equal to
a. Sum of individual resistances
b. Sum of the reciprocal of individual resistances
c. Reciprocal of the sum of individual resistances
d. All of these
ANSWER: Sum of the reciprocal of individual resistances
41) Permeability of a material is
a. Directly proportional to both flux density and magnetizing force
b. Directly proportional to flux density and inversely proportional to the magnetizing force
c. Directly proportional to the magnetizing force and inversely proportional to the flux density
d. Inversely proportional to both flux density and magnetizing force
ANSWER: Directly proportional to flux density and inversely proportional to the magnetizing force
42) The amount of flux density set up in the core is dependent upon
a. Current
b. No. of turns, cross sectional area of core
c. Materials of the magnetic core, length of core
d. All of these
ANSWER: All of these
43) When a solenoid attracts an iron bar,
a. They leave the south pole to go around to the north pole
b. They leave the north pole to go around to the south pole
c. They leave the north pole to go to infinity
d. They leave the south pole to go to the infinity
ANSWER: They leave the north pole to go around to the south pole
Electrical Basic Questions 13
44) If two conductors carrying currents in opposite direction are placed parallel to each other then the magnetic field set up by the conductors
a. Attract each other
b. Repels each other
c. Perpendicular to each other
d. Parallel to each other
ANSWER: Repels each other
45) According to the End Rule, the current directions when looked from one end of the coil if that end is South Pole and if the end is North Pole are
a. Both clockwise
b. Anticlockwise, clockwise
c. Clockwise, anticlockwise
d. Both anticlockwise
ANSWER: Clockwise, anticlockwise
46) When the flux crosses the air gap, it bulges outward at the ends of the air gap and the flux density in the air gap is reduced. This is known as
a. Leakage flux
b. Fringing
c. Relative permeability
d. Magnetizing force
ANSWER: FRINGING
Electrical Basic Questions 13
47) The induced emf sets up the direction of current in such a way that the magnetic field produced by it
a. Supports the cause producing it
b. Opposes the cause producing it
c. Increases
d. Decreases
ANSWER: Opposes the cause producing it
48) Which among the following sentences is correct?
a. Lenz’s law is used to find the direction of induced current
b. Fleming’s right hand rule is used to find the direction of induced current
c. Fleming’s left hand rule is used to find the direction of force
d. All of these
ANSWER: All of these
49) If the magnetic field is stationary and the conductor is in motion then the emf induced is called
a. Dynamically induced emf
b. Statically induced emf
c. Self induced emf
d. Mutually induced emf
ANSWER: Dynamically induced emf
50) The coefficient of coupling is given by
a. M / √(L2L1)
b. M / (L2 L1)
c. √(L2 L1) / M
d. (L2 L1) / M
ANSWER: M / √(L2L1)
Electrical Basic Questions 13
