1)Specific resistance of a conductor depends on
A)dimension of conductor
B)composition if conductor material
C)resistance of cinductor
D)both a & b
2)which of the following materials posses the least specific resistance?
A)aluminium
B)copper
C)silver
D)iron
3)the insulation resistance of a cable of length 10km is 1 Mohm.For a length of 100km of same cable,the insulation resistance will be
A)1
B)10
C)0.1
D)0.01
4)which of the following is an active element in a circuit?
A)current source
B)resistance
C)inductance
D)capacitance
5)twelve 1 ohm resistance ara used as edge of form a cube.The resistance between two diagonally opposite corners of the cube is
A)5/6
B)1
C)6/5
D)3/2
Answers. 1)D,2)C,3)C,4)A,5)A
1)Tha emf induced in a conductor rotating in a bipolar field is
A)DC
B)ac
C)DC and ac both
D)none if these
2)poles of DC machine are often laminated to
A)reduce pulsation loss
B)reduce armature reaction
C)reduce iron weight
D)dissipate more heat
3)the armature if DC machine is laminated
A)to reduce hysteresis loss
B)to reduce eddy current loss
C)to reduce the mass
D)to reduce the inductance
4)what are slot wedges in a DC machine made of ?
A)mild steel
B)silicon steel
C)fibre
D)cast iron
5)the commutator of a DC motor serves the purpose of
A)changing ac to DC
B)converting ac to DC
C)reducing friction
D)avoiding arc at the brushes
Answer: 1)B,2)A,3)B,4)C,5)D
1)the efficiency of a power transformer is around
A)59%
B)60%
C)80%
D)95%
2)A transformer steps up the voltage by a factor 100.The ratio of current in the primary to that in the secondary is
A)1
B)100
C)0.01
D)0.1
3)Transformation action requires a
A)constant magnetic flux
B)increasing magnetic flux
C)alternating magnetic flux
D)alternating electric flux
4)The inductive reactance of a transformer depends on
A)electromotive force
B)magnetomotive force
C)magnetic flux
D)leakage flux
5)A transformer is supplying pure resistive ( unity pf) load.The power factor on primary side will be
A)about 0.95(lead)
B)0.95(lag)
C)zero
D)unity
Answer:1)D,2)B,3)C,4)D,5)B
1)A smooth cylindrical synchronous motor will always stop when
A)excitation winding gets disconnected
B)load varies
C)supply voltage fluctuations
D)supply frequency varies
2)The speed of a synchronous motor can be varied by varying its
A)excitation
B)supply frequency
C)supply voltage
D)load
3)In a 3 phase synchronous motor,the magnitude of back emf set up in the stator depends on
A)rotor excitation
B)supply voltage
C)rotor speed
D)load on motor
4)Which motor can conveniently operate at lagging as well as leading power factor?
A)squirrel cage induction motor
B)wound rotor induction motor
C)synchronous motor
D)DC shunt motor
5)If the field excitation of a synchronous motor is under excited ,the power factor will be
A)lagging
B)leading
C)unity
D)more then unity
Answer:-1)A,2)B,3)A,4)C,5)A
A)dimension of conductor
B)composition if conductor material
C)resistance of cinductor
D)both a & b
2)which of the following materials posses the least specific resistance?
A)aluminium
B)copper
C)silver
D)iron
3)the insulation resistance of a cable of length 10km is 1 Mohm.For a length of 100km of same cable,the insulation resistance will be
A)1
B)10
C)0.1
D)0.01
4)which of the following is an active element in a circuit?
A)current source
B)resistance
C)inductance
D)capacitance
5)twelve 1 ohm resistance ara used as edge of form a cube.The resistance between two diagonally opposite corners of the cube is
A)5/6
B)1
C)6/5
D)3/2
Answers. 1)D,2)C,3)C,4)A,5)A
1)Tha emf induced in a conductor rotating in a bipolar field is
A)DC
B)ac
C)DC and ac both
D)none if these
2)poles of DC machine are often laminated to
A)reduce pulsation loss
B)reduce armature reaction
C)reduce iron weight
D)dissipate more heat
3)the armature if DC machine is laminated
A)to reduce hysteresis loss
B)to reduce eddy current loss
C)to reduce the mass
D)to reduce the inductance
4)what are slot wedges in a DC machine made of ?
A)mild steel
B)silicon steel
C)fibre
D)cast iron
5)the commutator of a DC motor serves the purpose of
A)changing ac to DC
B)converting ac to DC
C)reducing friction
D)avoiding arc at the brushes
Answer: 1)B,2)A,3)B,4)C,5)D
1)the efficiency of a power transformer is around
A)59%
B)60%
C)80%
D)95%
2)A transformer steps up the voltage by a factor 100.The ratio of current in the primary to that in the secondary is
A)1
B)100
C)0.01
D)0.1
3)Transformation action requires a
A)constant magnetic flux
B)increasing magnetic flux
C)alternating magnetic flux
D)alternating electric flux
4)The inductive reactance of a transformer depends on
A)electromotive force
B)magnetomotive force
C)magnetic flux
D)leakage flux
5)A transformer is supplying pure resistive ( unity pf) load.The power factor on primary side will be
A)about 0.95(lead)
B)0.95(lag)
C)zero
D)unity
Answer:1)D,2)B,3)C,4)D,5)B
1)A smooth cylindrical synchronous motor will always stop when
A)excitation winding gets disconnected
B)load varies
C)supply voltage fluctuations
D)supply frequency varies
2)The speed of a synchronous motor can be varied by varying its
A)excitation
B)supply frequency
C)supply voltage
D)load
3)In a 3 phase synchronous motor,the magnitude of back emf set up in the stator depends on
A)rotor excitation
B)supply voltage
C)rotor speed
D)load on motor
4)Which motor can conveniently operate at lagging as well as leading power factor?
A)squirrel cage induction motor
B)wound rotor induction motor
C)synchronous motor
D)DC shunt motor
5)If the field excitation of a synchronous motor is under excited ,the power factor will be
A)lagging
B)leading
C)unity
D)more then unity
Answer:-1)A,2)B,3)A,4)C,5)A
No comments:
Post a Comment