[amp_mcq option1=”Torque will remain constant” option2=”Torque will change but power will remain constant” option3=”shunt motor if the excitation is changed A. Torque will remain constant B. Torque will change but power will remain constant C. Torque and power both will change” option4=”Torque, power and speed, all will change” correct=”option3″]
The correct answer is: C. Torque and power both will change.
Explanation:
The torque of a DC shunt motor is proportional to the field current. When the excitation is changed, the field current changes, and the torque changes accordingly. The power of a DC shunt motor is proportional to the square of the armature current. When the excitation is changed, the armature current changes, and the power changes accordingly.
Here is a more detailed explanation of each option:
- Option A: Torque will remain constant. This is incorrect because the torque of a DC shunt motor is proportional to the field current. When the excitation is changed, the field current changes, and the torque changes accordingly.
- Option B: Torque will change but power will remain constant. This is incorrect because the power of a DC shunt motor is proportional to the square of the armature current. When the excitation is changed, the armature current changes, and the power changes accordingly.
- Option C: Torque and power both will change. This is the correct answer because the torque and power of a DC shunt motor are both proportional to the field current. When the excitation is changed, the field current changes, and the torque and power both change accordingly.
- Option D: Torque, power and speed, all will change. This is incorrect because the speed of a DC shunt motor is proportional to the applied voltage. When the excitation is changed, the speed does not change.