Braking of DC Motor MCQ [Free PDF] – Objective Question Answer for Braking of DC Motor Quiz

41. The shape of the current-torque current characteristics in DC series motor is a __________

A. Rectangular Hyperbolic
B. Parabola
C. Circle
D. Ellipse

Answer: B

The shape of the current-torque characteristics in the DC series motor is a parabola. The motor equation is

Eb=Vt-IaRa=Km∅ωm

T=Km∅Ia

∅∝Ia

T∝Ia2.   

 

42. Calculate the current in DC series field winding using the following data: Ia=3 A.

A. 4 A
B. 2 A
C. 3 A
D. 6 A

Answer: C

In a DC series motor, field windings are connected in series with the armature circuit. The armature current will also flow through the series winding.

If=Ia=3 A.   

 

43. For a given torque, increasing diverter resistance of a DC series motor causes the ________

A. decrease in speed and less armature current
B. a decrease in speed but armature current remains the same
C. increase in speed and more armature current
D. increase in speed but armature current remains the same

Answer: A

In DC series motor, increasing diverter resistance increases the field current and field flux and also decreases the armature current and therefore decreases the speed.   

 

44. The field diverter resistance for a DC series motor is kept ________

A. High
B. Low
C. zero
D. one

Answer: B

The field diverter resistance for a DC series motor is kept low in order to increase the speed of the motor. This will reduce the field flux and increase the armature current.   

 

45. Order of the circuit is the number of memory elements present in the circuit.

A. True
B. False

Answer: A

The order of the circuit is the number of memory/storing elements that are non-separable present in the circuit. Examples of memory elements are capacitors and inductors.

 

46. In Induction motor rotor laminations are thicker than stator laminations.

A. True
B. False

h({});
Answer: A

The lamination thickness depends upon the frequency. The rotor frequency is s×f where f is stator supply frequency. The rotor laminations are thicker than stator laminations because rotor frequency is less.   

 

47. Choose the Induction motor with peak speed.

A. 10 Pole
B. 12 Pole
C. 14 Pole
D. 16 Pole

Answer: A

The synchronous speed of the Induction motor is

Ns=120×f÷P.

Ns∝(1÷P).

The synchronous speed is inversely proportional to the pole. The maximum speed will be achieved with a minimum number of poles.   

 

48. Which starting method is the best method for Induction motor?

A. Direct online starting
B. Autotransformer starting
C. Reactance starting
D. Star-Delta starting

Answer: D

The Star-Delta starting method is one of the best methods for starting the Induction motor. This method is cheaper and the line current in the star is 1÷3 times of in delta connection.   

 

49. Induction motor is analogous to __________

A. Transformer
B. DC machine
C. Synchronous motor
D. Synchronous generator

Answer: A

The Induction motor is analogous to the transformer. It is also known as a rotating transformer. Both work on the principle of electromagnetic induction.   

 

50. Which type of Induction motor is best for the pole changing method?

A. SCIM
B. WRIM
C. Single-phase IM
D. Linear IM

Answer: A

Pole changing method is used to control the speed of the Induction motor. It is only applicable for SCIM because the SCIM rotor is made up of aluminum, and copper bars.   

Scroll to Top