1. In aircraft industry, the material used for the conductor is
a) aluminium
b) copper
c) silver
d) iron
ans. a
2. Which of the following class is mainly used in electrical machines for insulation
a) class Y
b) class A
c) class F
d) class C
ans. b
3. The resistance of insulating material is
a) proportional to its resistivity
b) inversely proportional to its resistivity
c) independent of the temperature
d) none of these
ans. a
4. when a substance is placed in a magnetic field , its ability to get magnetized depends upon its
a) permeability
b) permitivity
c) susceptibility
d) none of these
ans. c
5. The material used for manufacture of armature covers of dc motors and dynamos should have
a) small B-H loop area
b) large B-H loop area
c) very large B-H loop area
d) none of these
ans. a
6. For steady flux and good mechanical properties, the material extensively used for magnetic circuit is
a) iron
b) cast iron
c) grey cast iron
d) cast steel
ans. c
7. When 3-phase synchronous motor is switched on. there exists a rotating magnetic field. The magnitude of this field flux
a) is constant at all loads
b) varies with load
c) varies with power factor
d) none of these
ans. a
8. When the excitation of synchronous motor is varied
a) the pf and the armature current varies
b) the pf varies but the armature current does not vary
c) the armature current varies but the pf does not vary
d) neither the pf nor the armature current varies
ans. a
a) aluminium
b) copper
c) silver
d) iron
ans. a
2. Which of the following class is mainly used in electrical machines for insulation
a) class Y
b) class A
c) class F
d) class C
ans. b
3. The resistance of insulating material is
a) proportional to its resistivity
b) inversely proportional to its resistivity
c) independent of the temperature
d) none of these
ans. a
4. when a substance is placed in a magnetic field , its ability to get magnetized depends upon its
a) permeability
b) permitivity
c) susceptibility
d) none of these
ans. c
5. The material used for manufacture of armature covers of dc motors and dynamos should have
a) small B-H loop area
b) large B-H loop area
c) very large B-H loop area
d) none of these
ans. a
6. For steady flux and good mechanical properties, the material extensively used for magnetic circuit is
a) iron
b) cast iron
c) grey cast iron
d) cast steel
ans. c
7. When 3-phase synchronous motor is switched on. there exists a rotating magnetic field. The magnitude of this field flux
a) is constant at all loads
b) varies with load
c) varies with power factor
d) none of these
ans. a
8. When the excitation of synchronous motor is varied
a) the pf and the armature current varies
b) the pf varies but the armature current does not vary
c) the armature current varies but the pf does not vary
d) neither the pf nor the armature current varies
ans. a
