121. If the applied voltage to a dc machine is 230V, then the back emf, for maximum power developed is
- 115 V
- 200 V
- 230 V
- 460 V
122. The efficiency of a dc motor when developing maximum power will be about
- 100%
- 50%
- less than 50%
- more than 50%
123. Torque developed in a dc motor depends upon
- magnetic field
- current flowing through the armature conductors
- active length of the conductors
- number of armature conductors
- radius of armature
- all of these factors
124. In a dc series motor, the torque developed is
- inversely proportional to armature current
- directly proportional to armature current
- proportional to the square of armature current
- proportional to the square root of the armature current
125. Torque developed by the armature of a dc motor is proportional to which one of the following?
- (Back emf) x (Armature current)
- (Magnetic flux per pole) x (Armature current)
- (Back emf) x (Magnetic flux per pole)
- (Back emf) / (Magnetic flux per pole)
126. In an electric motor, the electromagnetic torque developed is
- in opposite direction to both load torque and frictional torque
- in the same direction as the load torque but in opposite direction to frictional torque
- in the same direction as the load torque and frictional torque
- in the same direction as the frictional torque but in the opposite direction to the load torque
127. The torque-speed characteristic of a dc shunt motor is
- a rectangular hyperbola
- a drooping straight line
- a parabola
- none of the above
128. The horse power obtained from the motor shaft is called the
- IHP
- BHP
- useful output
- none of these
129. In a dc motor, the shaft torque is less than armature torque. This is due to
- eddy current loss
- hysteresis loss
- stray loss
- all of the above
130. In a dc motor if the brushes are given a backward shift, then
- commutation is improved
- speed increases
- speed remains unaffected
- both (1) and (2)
Please ,send the answer because I need answer to correct my result
Click the “correct answer” under each question to see the answer.