1. The armature mmf wave of a dc machine is
a) sinusoidal and depends on the speed
b) square and independent of speed
c) sinusoidal and independent of speed
d) triangular and independent of speed
ans. d
2. The armature mmf wave for a dc machine is
a) sinusoidal and rotates wrt armature
b) sinusoidal and rotates wrt field
c) triangular and rotates wrt armature
d) triangular and stationary wrt armature
ans. c
3. Rotational losses in electrical machines consists of
a) friction and windage losses
b) stator core , friction and windage losses
c) rotor core, friction and windage losses
d) stray load losses and friction and windage losses
ans. c
4. Efficiency of electrical machines should be calculated by measuring
a) output and input
b) losses and output
c) losses and input
d) losses
ans. d
5. Electrical machines are designed to have maximum efficiency at
a) full load
b) 50% of full load
c) near about full load
d) no load
ans. c
6. In 3-phase ac machines, phase spread of 120 degrees is preferred over a phase spread of 60 degrees
a) true
b) false
c) depends upon type of machine
d) none of these
ans. b
7. The mmf produced by a single phase winding is
a) pulsating and stationary
b) pulsating and rotating
c) constant in amplitude and stationary
d) constant in amplitude and rotating
ans. a
8. The material used for magnetic circuit where high value of flux density required is
a) cast iron
b) ferro cobalt
c) soft steel
d) gray cast iron
ans. b
9. The material suitable for the manufacture of transformer and large turbo-alternator is
a) hot rolled grain oriented steel
b) cold rolled grain oriented steel
c) cast steel
d) none of these
ans. b
10. The material used for the magnetic circuit where high value of flux density required is
a) cast iron
b) ferro cobalt
c) soft steel
d) gray cast iron
ans. b
a) sinusoidal and depends on the speed
b) square and independent of speed
c) sinusoidal and independent of speed
d) triangular and independent of speed
ans. d
2. The armature mmf wave for a dc machine is
a) sinusoidal and rotates wrt armature
b) sinusoidal and rotates wrt field
c) triangular and rotates wrt armature
d) triangular and stationary wrt armature
ans. c
3. Rotational losses in electrical machines consists of
a) friction and windage losses
b) stator core , friction and windage losses
c) rotor core, friction and windage losses
d) stray load losses and friction and windage losses
ans. c
4. Efficiency of electrical machines should be calculated by measuring
a) output and input
b) losses and output
c) losses and input
d) losses
ans. d
5. Electrical machines are designed to have maximum efficiency at
a) full load
b) 50% of full load
c) near about full load
d) no load
ans. c
6. In 3-phase ac machines, phase spread of 120 degrees is preferred over a phase spread of 60 degrees
a) true
b) false
c) depends upon type of machine
d) none of these
ans. b
7. The mmf produced by a single phase winding is
a) pulsating and stationary
b) pulsating and rotating
c) constant in amplitude and stationary
d) constant in amplitude and rotating
ans. a
8. The material used for magnetic circuit where high value of flux density required is
a) cast iron
b) ferro cobalt
c) soft steel
d) gray cast iron
ans. b
9. The material suitable for the manufacture of transformer and large turbo-alternator is
a) hot rolled grain oriented steel
b) cold rolled grain oriented steel
c) cast steel
d) none of these
ans. b
10. The material used for the magnetic circuit where high value of flux density required is
a) cast iron
b) ferro cobalt
c) soft steel
d) gray cast iron
ans. b
