Question: The purpose of retardation test on D.C. shunt machines is to find out____________?

• 1. stray losses
• 2. eddy current losses
• 3. field copper losses
• 4. windage losses

Question: Which of the following tests will be suitable for testing two similar D.C. series motors of large capacity ?

• 1. Swinburne’s test
• 2. Hopkinson’s test
• 3. Field test
• 4. Brake test

Question: Hopkinson’s test on D.C. machines is conducted at_______________?

• 1. no-load
• 2. part load
• 3. full-load
• 4. overload

Question: For which types of D.C. motor, dynamic braking is generally used ?

• 1. Shunt motors
• 2. Series motors
• 3. Compound motors
• 4. All of the above

Question: Which method of braking is generally used in elevators ?

• 1. Plugging
• 2. Regenerative braking
• 3. Rheostatic braking
• 4. None of the above

Question: In variable speed motor___________?

• 1. a stronger commutating field is needed at low speed than at high speed
• 2. a weaker commutating field is needed at low speed than at high speed
• 3. same commutating field is needed at low speed than at high speed
• 4. none of the above is correct

Question: When the armature of a D.C. motor rotates, e.m.f. induced is___________?

• 1. self-induced e.m.f.
• 2. mutually induced e.m.f.
• 3. back e.m.f
• 4. none of the above

Question: Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control______________?

• 1. drum type controller is used
• 2. three point starter is used
• 3. four point starter is used
• 4. all above can be used

Question: If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens____________?

• 1. this will make armature to take heavy current, possibly burning it
• 2. this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
• 3. nothing will happen to motor
• 4. motor will come to stop

Question: D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the________________?

• 1. series motor
• 2. shunt motor
• 3. compound motor
• 4. any of the above