Tuesday, June 28, 2016

T10 Quiz DC Machine Phase -1



Q1:- To develop the electromagnetic force and/or torque in electro mechanical energy conversion system act in a direction that tends 
  1. to increase the stored energy at constant flux
  2. to decrease the stored energy at constant flux 
  3. to decrease the coenergy at constant mmf
  4. to decrease the stored energy at constant mmf
ANSWER:-2




Q2:- What is the effect produced by the electric current in an electric motor?

  1. magnetic effect only
  2. magnetic as well as heating effect 
  3. heating efeect only
  4. heating as wel as chemical effect.
ANSWER:-2




Q3:- The rotating part of d.c. motors is known as 

  1. pole
  2. stator
  3. armature
  4. carbon brush
ANSWER:-3




Q4:-If the current carrying coil is placed in a uniform magnetic field direction of magnetic induction then

  1. the net force and torque on the coil are both zero
  2. the net force is zero but torque is finite
  3. the net force is finite but torque is zero
  4. the net force and torque are both finite
ANSWER:-1




Q5:-Why is the air gape b/w the yoke and armature of an electric motor kept smalle?

  1. to achieve a stronger magnetic field
  2. to avoid overheating of the machine
  3. to make sataion easier
  4. none
ANSWER:-1





Q6:-The function of the commutator in a d.c. machine is ?

  1. to change alternating current to direct current 
  2. to improve commutation
  3. for easy speed control
  4. to change alternating voltage to direct voltage 
ANSWER:-4





Q7:- Carbon brushes are used in electrical motors to 

  1. brush off carbon deposits on the commutator
  2. provide a path for flow of current 
  3. prevent overheating of armature winding
  4. prevent sparking during commutation
ANSWER:-2



Q8:-D.C. shunt generator has 

  1. slightly drooping characteristics
  2. appreciable rising characteristics
  3. constant voltage charactersitics
  4. appreciable falling characteristics
ANSWER:-1





Q9:- which of the following generator is used for charging batteries?

  1. compound generators
  2. shunt generators
  3. series generators
  4. tacho generators
ANSWER:-2




Q10:- Conditions for maximum power output for a d.c. motor is 

  1. back emf =applied voltage
  2. back emf= half of applied voltage
  3. back emf= armature current*armature resistance
  4. back emf =0.5 *armature current 
ANSWER:-2



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