Hi All,
Please find the previous bits to test your knowledge in DC.Generators,DC motors,3-phase induction motors ,basic instruments..Please read the concepts first then solve the bits..
Answers will be posted later....
BEE
JNTUH PREVIOUS BITS
UNIT-5(DC generators)
1. The Commutator in a dc
machine can be convert [ ]
(a) ac to dc (b) dc to ac (c) both a and b
(d) None of the above
2. The emf produced in the dc
generator is ____ induced emf [ ]
(a) Statically (b) Dynamically (c)
magnetically (d) Electrostatically
3. DC generator operates on
the principle of [ ]
(a) Electromagnetic induction (b) Lenz's law (c) Biot
Savart's law (d) none of these
4. Emf equation of generator is ____________________
5. Yoke is
made of which material______________
6. Types of
windings in dc generator_______________________
7. The Mechanical energy source
used to drive a dc generator is called a [ ]
(A) Rotor (B) Prime Mover (C) Alternator (D) Motor drive
8. The nature of current
having in the armature of a dc machine is _____ [ ]
a) AC b) DC c) pulsating d) None
9. The induced voltage in a
single loop reverses_____ [ ]
a) Once each revolution b) once each half
revolution
c) one each quarter revolution d) 8 times each revolution
10. The field of self excited
generator is excited by [ ]
a) Dc b) Ac c) By its own current d) Either ac or Dc
11. The magnetic field which initially induces emf in the armature in
a self excited dc generator is
Because of ___________________
12. Emf induced in each
conductor of a DC Machine is [ ]
A) An alternating emf B) A direct emf
C) A pulsating emf D) Emf of random waveshape
13. The residual magnetism of a
DC shunt generator can be regained by [ ]
A) Connecting the shunt field to a battery
B) Running the generator on no load for sometime
C) Grounding the shunt field D) Reversing the direction of
rotation of the generator.
14. __________________ Law states that the magnitude of individual emf
is equal to the rate of
Change of flux linkages.
15. A four pole DC generator is running at 1500 rpm. The frequency of
current in the armature is ______________________.
16. The armature of a dc machine is a laminated to
reduce _____________________________.
17. The function of
interpoles in a dc machine is to________________
18. The EMF induced in
a coil rotating in a uniform magnetic field is maximum when the flux linkage by
the coil is _______________
UNIT-5(DC Motors)
1. The Commutator in a dc
machine can be convert [ ]
(a) ac to dc (b) dc to ac (c) both a and b (d) None of
the above
2. Fleming's left hand rule is
applicable for: [ ]
(a) dc generator (b) dc motor (c) alternator (d) Transformer
3. The armature torque of the
dc shunt motor is proportional to [ ]
(a) armature current only (b) field flux
only (c) armature current and flux both (d) None
4. Motor which should not run
at no-load is [ ]
(a) Series motor (b) shunt motor (c)
compound motor (d) induction motor
5. Yoke
is made of which material______________
6. Losses in DC machine
are_______________________
7. Types of DC
motors___________ ___________________________
8. In DC shunt motor the Torque
is directly propotional to __________________
9. High permeability magnetic
materials helps [ ]
A) To confine the flux within the
magnetic circuit. B) To allow the flux to leak
C) In producing more
current. D) None of the
10. A Commutator in a DC machine can convert ____
to ______ [ ]
(a) AC, DC (b) DC, AC (c) either ‘A’ or ‘B’
(d) None
11. The current flowing through armature
conductors of a dc motor is _____________ [ ]
a) Pulsating b) Dc c) Ac
d) none of these
12. In Swinburne’s test of a Dc machine [ ]
a) No load
losses are calculated and copper losses are measured
b) No load
losses are measured and copper losses are calculated
c) Both the
losses are measured
d) Both the losses are calculated
13. The supply terminals for a dc shunt motor are
reversed. What will be effect on the motor [ ]
a) It will run as Dc
generator b) runs in reverse direction c)it stops d)its burns
14. The starting
resistance for a dc shunt motor_____________
15. A 3 point starter
is considered suitable for dc______________ motor
16. The magnitude of force acting on a current
carrying conductor placed in a magnetic field is
independent of [ ]
A) Flux density B) length of conductor
C) cross-sectional area of
conductor D) current flowing Through the conductor
17. When a dc machine is connected in the dc
supply main it will produce [ ]
A) Emf in opposition to applied voltage. B)
Unidirectional torque
C) Copper losses in the
windings D) all of the above
18. Emf induced in each conductor of a DC Machine
is [ ]
A) An alternating emf B) A direct emf
C) A pulsating emf D) Emf
of random waveshape
19. The starting torque of a dc shunt motor is [ ]
A) Zero B) low C) high D)
very high.
20. The armature of a dc machine is a
laminated to reduce _____________________________.
21. If the flux of a dc motor approaches zero its
speed will_______________________.
22. The direction of mechanical force
experienced on a current carrying conductor placed in a magnetic Field is determined by _______________________________
23. The function of
interpoles in a dc machine is to________________
24 The speed of a DC motor is directly
proportional to its ________________ and inversely proportional
to______________________
25. The current drawn
by a dc motor at the starting instant will be________
26. The eddy current losses is directly
proportional to [ ]
a) f b)f^2 c)f^1.6 d)f^3
27. The iron losses [ ]
a) core losses b)
eddycurrent losses c) hystersis losses d) all the above
28. The speed of a d.c motor can be controlled by
varying [ ]
a)its flux per pole b)resistance of
armature circuit c)applied voltage d)all the above
29. The collection of current from armature conductors to the external
load is the function of---------------------
30. The iron or core losses are also known as------losses
31. In d.c motor
unidirectional torque is produced with the help of---------------and
commutator.
32. Between no load
and full load -------motor develops the least torque
33. Under constant
load conditions ,the speed of a d.c motor is affected by---------------
34. The Eb/V ratio of a d.c motor known as
----------------
35.An invertor is employed
to convert--------------voltage to -----------------voltage
UNIT-7: 3-phase induction
motors
1. Difference in speed between
stator field and rotor [ ]
(a) Full load speed (b)No load speed
(c)Slip (d) Regulation
2. When rotor is at standstill [ ]
(a) slip is zero (b) slip is one (c) Any
slip (d) Slip is infinity
3. Slip=_______________
4. Types of rotors in 3-phase induction
motor ___________________
5. The
relationship between rotor frequency, f2, slip (s) and the stator frequency
(f1) is = _______
6. The speed of rotor field of an Induction Motor
is ______
7. The synchronous speed of
50 Hz, 4 pole induction motor is _____________________.
8. The value of slip of Induction motor at
synchronous speed will be ___
9. An induction motor works with _____. [ ]
a) DC only b) AC only c)
both AC & DC d) None
10.In
an Induction motor, the torque is related to supply voltage as ___________
11. The synchronous speed
of a 2 pole 3 phase induction motor for supply frequency of 60 Hz is ___
12. The number of slip rings on a 3 phase
wound rotor induction motor is ____ . [ ]
a) 3 b) 2 c) 6 d) None
Unit-8: Basic instruments.
1. PMMC is used for measuring [
]
(a) DC (b)AC (c)
AC&DC (d)None
2. MI instrument is used to
measure [ ]
(a) AC (b) DC (c)
AC&DC (d) NONE
3. Example of absolute instrument ________________________
4. Example of integrating
instrument_______________
5. An ohm-meter is an ____ type instrument.
[ ]
a) Dynamo meter b) moving coil c) Moving
iron d) Induction
6. A meter that is capable of measuring DC
only is ____ [ ]
a) Moving Coil b) Moving Iron c) Thermo
Couple d) None
7. When the instrument is over damped it will become ____ -
8. An instrument that measures electrical energy is
an ____ type instrument
9. The damping usually provided in indicating
instruments having weak magnetic field is [ ]
a) air friction b) fluid
friction c) hysteresis d) eddy current
10. Gravity controlled
instruments are always used in _____________ position
11. In indicating instruments the damping is
usually adjusted [ ]
a)at
critical value b) to the value slightly higher than critical value
c)to the value slightly
below critical value d) to any value
12. A Moving iron ammeter, when used on AC
circuit, indicates ____ value of current.
13. In gravity
control, the controlling torque is a function of angular deflection, as _____.