Jan18 WIREMAN THEORY
SEMESTER -III
One that is based on forward biased PN junction is-
a) Photo diode
b) LED
c) Photo voltaic cell
d) Both (a) and (b)
Which of these is a best
description of a zener diode?
a) it operates in the reverse region
b) It is a constant voltage device
c) It is a constant current device
d) None of these
The LED is usually made of material like-
c) GeAs
b) C and Sl
d) None of these
Zener diode are used as-
a) Reference voltage element
b) Reference current element
c) Reference resistance
d) None of these
Zener diode are -
a) Specially doped p n junction
b) Normally doped p -- n junction
c) Lightly doped junction
d) None of these
ICs are generally made of
a) Silicon
b) Germanium
c) Copper
d) Nonc of these
The active components in an IC are
a) Resistors
b) Capacitors
c) Transistors and diodes
d) None of these
Diode characteristic curve is a plot between-
a) Current and time
b) Voltage and time
c) Voltage and current
d) Both (a) & (b)
in case a PN junction is forward biased-
a) Hole and electrons seize to move
b) Electrons and holes move towards the junction
c) Electrons and holes move away from the junction
d) Depletion region decreases
The element that has the biggest size in a transistor is
a) Collector
b) Base
c) Emitter
d) Collector-base-junction
The value of a of a transistor is
a) More than 1
b) Less than 1
d) None of these
The voltage gain in a transistor comected in arrangement is the highest.
a) Common base
b) Common collector
c) Common emitter
d) None of these
A SCR is switch.
a) One directional
b) Two directional
c) Three directional
d) Four directional
A silicon controlled rectifier (SCR) is a-
a) Unijunction device
b) Device with three junctions
c) Device with four junctions
d) None of these
Which of the following finds applications in speed control of D.C. motor?
a) FET
b) NPN transistor
c) SCR
d) None of these
A UJT has
a) Two pn junction
b) One pn junction
c) Three pn junction
d) None of these
The fuse rating is expressed in terms of-
a) Current
b) Voltage
c) VAR
d) KVA
MCCB are commonly used for operating current between-
a) 63 amps. To 800 amps
b) 5 amps. To 16 amps
c) 16 amps. To 32 amps
d) None ofthese
ELCB is an abbreviation for-
a) Electrolytic circuit breaker
b) Earth locking circuit breaker
c) Earth leakage circuit breaker
d) Electric leakage circuit breaker
Miniature circuit breaker is a small-
a) Fuse
b) Magnetic switch
c) Electromagnetic switch
d) Two way switch
For soldering of platinum, tungsten, steel etc. the solder used is-
a) Cabmium-solder
b) Tin lead solder
c) Tin lead silver solder
d) Copper silver - zinc solder
The following magnet is used in large machines to create magnetic flux-
a) Permanent magnet
b) Electro magnet
c) Temporary magnet
d) Any of these
Function ofis to collect current from the commutator and supply it to the external load.
a) Field magnet
b) Armature
c) Brushes
d) Yoke
Which of the following generators have two field windings?
a) Series wound generator
b) Shunt wound generator
c) Compound wound generator
d) All of these
In a separately excited D.C generator the field is connected to-
a) In series with an armature
b) Across the armature
c) To the external supply source
d) None of these
The armature reaction in D.C machine causes distortion in the main field flux. This effect of armature reaction can be reduced by-
a) Increasing the length of air gap b) Decreasing the length of air gap
c) Increasing the number of poles
d) Decreasing the number of poles
In a dc generator the polarity of interpole is-
a) Always N
b) Always S
c) Same as the polarity of the main pole that follows in the direction of rotation
d) Same as the polarity of the main pole that proceeds in the direction of rotation
The function of the commutator in a D.C machine is-
a) To change ac to dc
b) To change alternating voltage to direct voltage
c) For easy control of voltage
d) None of the above
Winding generator will have„
a) Wave wound
b) Lap wound
c) Delta wound
d) Duplex wound
The efficiency of a DC shunt generator has a maximum value when-
a) Magnetic losses are equal to mechanical losses
b) Armature copper loss is equal to the constant loss
c) Field copper loss is equal to the constant loss.
d) None of the above
For parallel operation the generators normally preferred are-
a) Series generator
b) Shunt generator
c) Compound generator
d) Series and shunt generator
Interpoles in the armature of a D.C generator are used to-
a) Neutralize the reactance voltage
b) Neutralize the reactance voltage and the cross-magletizing effect of the armature reaction
c) Neutralize the cross-magnetizing effect of the armature reaction
d) None of the above
Which DC motor has approximately constant speed?
a) Series
b) Shunt
c) Cumulatively compound motor
d) All of these
A series motor-
a) Should always be started on load
b) Always runs at constant speed
c) Is not suitable for high starting torque
d) May 'run away' if the field gets opened
The back emf of a DC motor depend on-
a) Field flux
b) Shape of conductors
c) Type of slip rings
d) Brush material
The electromagnetic torque and speed are in the same direction in case of-
a) DC motors
b) DC generators
c) Both DC motors as well as DC generators
d) None of the above
In DC motor, the conditions for maximum power is-
a) Supply voltage = h x back e.m.f.
b) Supply voltage = 4x back e.m.f.
c) Supply voltage = 2 x supply voltage
d) Supply voltage = h x supply voltage
The speed of a DC motor is-
a) Always constant
b) Directly proportional to back e.m.f.
c) Pirectly proportional to flux
d) Directly proportional to the product of' back eurnf. and flux
The direction of rotation of a compound dc motor can be effectively reversed by interchanging-
a) Shunt field connections
b) Series field connections
c) Armature connection
d) Line leads
Two wattmeter connected to measure the power in a balanced 3 phase load will indicate same reading when load p.f. is -
a) Zero
b) Unity
d) None of these
In a 3 phase, 4 wire star-connected system the voltage across the phases is . ...volts.
a) 400
b) 200
c) 500
d) None of these
In a balance 3-phase load, the current in the neutral will be
The rating of Alternator / Generator may be expressed in
c) KVAR
b) kva
Single phase motor generally used for small air compressor is-
a) Capacitor start and capacitor run motor
b) Reluctance motor
c) Universal motor
d) Shaded pole motor
A capacitor start, capacitor run single phase induction motor is basically a-
a) AC series motor
b) 2 Phase induction motor
c) 3 Phase induction motor
d) DC series motor
A three phase slip ring induction motor has-
a) Short Circuited rotor
b) Double cage rotor
c) Wound rotor
d) All of these
Switch not used in the house wiring circuit is -
a) Single way switch
b) Push button switch
c) Two way switch
d) Knife switch
The direction of rotation of 3 phase induction motor can be reversed by-
a) Reducing load
b) Reducing frequency
c) Supplying low voltage
d) Interchanging any two phases
Slip ring induction motors are employed only for-
a) Speed control
b) High starting torque
c) Both (a) and (b)
d) None of these
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 the above
SEMESTER -III
One that is based on forward biased PN junction is-
a) Photo diode
b) LED
c) Photo voltaic cell
d) Both (a) and (b)
Which of these is a best
description of a zener diode?
a) it operates in the reverse region
b) It is a constant voltage device
c) It is a constant current device
d) None of these
The LED is usually made of material like-
c) GeAs
b) C and Sl
d) None of these
Zener diode are used as-
a) Reference voltage element
b) Reference current element
c) Reference resistance
d) None of these
Zener diode are -
a) Specially doped p n junction
b) Normally doped p -- n junction
c) Lightly doped junction
d) None of these
ICs are generally made of
a) Silicon
b) Germanium
c) Copper
d) Nonc of these
The active components in an IC are
a) Resistors
b) Capacitors
c) Transistors and diodes
d) None of these
Diode characteristic curve is a plot between-
a) Current and time
b) Voltage and time
c) Voltage and current
d) Both (a) & (b)
in case a PN junction is forward biased-
a) Hole and electrons seize to move
b) Electrons and holes move towards the junction
c) Electrons and holes move away from the junction
d) Depletion region decreases
The element that has the biggest size in a transistor is
a) Collector
b) Base
c) Emitter
d) Collector-base-junction
The value of a of a transistor is
a) More than 1
b) Less than 1
d) None of these
The voltage gain in a transistor comected in arrangement is the highest.
a) Common base
b) Common collector
c) Common emitter
d) None of these
A SCR is switch.
a) One directional
b) Two directional
c) Three directional
d) Four directional
A silicon controlled rectifier (SCR) is a-
a) Unijunction device
b) Device with three junctions
c) Device with four junctions
d) None of these
Which of the following finds applications in speed control of D.C. motor?
a) FET
b) NPN transistor
c) SCR
d) None of these
A UJT has
a) Two pn junction
b) One pn junction
c) Three pn junction
d) None of these
The fuse rating is expressed in terms of-
a) Current
b) Voltage
c) VAR
d) KVA
MCCB are commonly used for operating current between-
a) 63 amps. To 800 amps
b) 5 amps. To 16 amps
c) 16 amps. To 32 amps
d) None ofthese
ELCB is an abbreviation for-
a) Electrolytic circuit breaker
b) Earth locking circuit breaker
c) Earth leakage circuit breaker
d) Electric leakage circuit breaker
Miniature circuit breaker is a small-
a) Fuse
b) Magnetic switch
c) Electromagnetic switch
d) Two way switch
For soldering of platinum, tungsten, steel etc. the solder used is-
a) Cabmium-solder
b) Tin lead solder
c) Tin lead silver solder
d) Copper silver - zinc solder
The following magnet is used in large machines to create magnetic flux-
a) Permanent magnet
b) Electro magnet
c) Temporary magnet
d) Any of these
Function ofis to collect current from the commutator and supply it to the external load.
a) Field magnet
b) Armature
c) Brushes
d) Yoke
Which of the following generators have two field windings?
a) Series wound generator
b) Shunt wound generator
c) Compound wound generator
d) All of these
In a separately excited D.C generator the field is connected to-
a) In series with an armature
b) Across the armature
c) To the external supply source
d) None of these
The armature reaction in D.C machine causes distortion in the main field flux. This effect of armature reaction can be reduced by-
a) Increasing the length of air gap b) Decreasing the length of air gap
c) Increasing the number of poles
d) Decreasing the number of poles
In a dc generator the polarity of interpole is-
a) Always N
b) Always S
c) Same as the polarity of the main pole that follows in the direction of rotation
d) Same as the polarity of the main pole that proceeds in the direction of rotation
The function of the commutator in a D.C machine is-
a) To change ac to dc
b) To change alternating voltage to direct voltage
c) For easy control of voltage
d) None of the above
Winding generator will have„
a) Wave wound
b) Lap wound
c) Delta wound
d) Duplex wound
The efficiency of a DC shunt generator has a maximum value when-
a) Magnetic losses are equal to mechanical losses
b) Armature copper loss is equal to the constant loss
c) Field copper loss is equal to the constant loss.
d) None of the above
For parallel operation the generators normally preferred are-
a) Series generator
b) Shunt generator
c) Compound generator
d) Series and shunt generator
Interpoles in the armature of a D.C generator are used to-
a) Neutralize the reactance voltage
b) Neutralize the reactance voltage and the cross-magletizing effect of the armature reaction
c) Neutralize the cross-magnetizing effect of the armature reaction
d) None of the above
Which DC motor has approximately constant speed?
a) Series
b) Shunt
c) Cumulatively compound motor
d) All of these
A series motor-
a) Should always be started on load
b) Always runs at constant speed
c) Is not suitable for high starting torque
d) May 'run away' if the field gets opened
The back emf of a DC motor depend on-
a) Field flux
b) Shape of conductors
c) Type of slip rings
d) Brush material
The electromagnetic torque and speed are in the same direction in case of-
a) DC motors
b) DC generators
c) Both DC motors as well as DC generators
d) None of the above
In DC motor, the conditions for maximum power is-
a) Supply voltage = h x back e.m.f.
b) Supply voltage = 4x back e.m.f.
c) Supply voltage = 2 x supply voltage
d) Supply voltage = h x supply voltage
The speed of a DC motor is-
a) Always constant
b) Directly proportional to back e.m.f.
c) Pirectly proportional to flux
d) Directly proportional to the product of' back eurnf. and flux
The direction of rotation of a compound dc motor can be effectively reversed by interchanging-
a) Shunt field connections
b) Series field connections
c) Armature connection
d) Line leads
Two wattmeter connected to measure the power in a balanced 3 phase load will indicate same reading when load p.f. is -
a) Zero
b) Unity
d) None of these
In a 3 phase, 4 wire star-connected system the voltage across the phases is . ...volts.
a) 400
b) 200
c) 500
d) None of these
In a balance 3-phase load, the current in the neutral will be
The rating of Alternator / Generator may be expressed in
c) KVAR
b) kva
Single phase motor generally used for small air compressor is-
a) Capacitor start and capacitor run motor
b) Reluctance motor
c) Universal motor
d) Shaded pole motor
A capacitor start, capacitor run single phase induction motor is basically a-
a) AC series motor
b) 2 Phase induction motor
c) 3 Phase induction motor
d) DC series motor
A three phase slip ring induction motor has-
a) Short Circuited rotor
b) Double cage rotor
c) Wound rotor
d) All of these
Switch not used in the house wiring circuit is -
a) Single way switch
b) Push button switch
c) Two way switch
d) Knife switch
The direction of rotation of 3 phase induction motor can be reversed by-
a) Reducing load
b) Reducing frequency
c) Supplying low voltage
d) Interchanging any two phases
Slip ring induction motors are employed only for-
a) Speed control
b) High starting torque
c) Both (a) and (b)
d) None of these
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 the above
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