Electrical Engineering XYZ

On what factors the speed of dc motor depends:

- Armature current Ia
- Applied voltage
- Field flux
- All of these

Correct answer: 4. All of these

Explanation:

**Armature current (Ia)**: The speed of a DC motor is directly proportional to the armature current. Increasing the armature current typically increases the motor’s torque, which results in higher speed, assuming other factors remain constant. Therefore, the armature current plays a significant role in determining the speed of a DC motor.**Applied voltage**: The speed of a DC motor is also directly influenced by the voltage applied to it. Increasing the applied voltage increases the electrical power supplied to the motor, which in turn increases the motor’s speed, assuming the load torque remains constant. So, the applied voltage is a crucial factor affecting the speed of a DC motor.**Field flux**: The field flux, determined by the field current or excitation, affects the motor’s back EMF (electromotive force). Back EMF opposes the applied voltage and affects the armature current, which in turn influences the motor’s speed. By adjusting the field flux, either by varying the field current or using a separately excited or permanent magnet field, the speed characteristics of the motor can be controlled.