What is the torque equation of a DC motor?
A
T = Eb × Iₐ B
T = k × Φ × Iₐ C
T = V × Iₐ D
T = Φ × N
Analysis & Theory
The torque (T) produced in a DC motor is directly proportional to the flux (Φ) and armature current (Iₐ).
In the torque equation T = k × Φ × Iₐ, what does 'Φ' represent?
A
Voltage B
Speed C
Magnetic flux per pole D
Resistance
Analysis & Theory
‘Φ’ stands for magnetic flux per pole, which influences the torque in a DC motor.
What happens to torque if the armature current (Iₐ) is doubled, assuming constant flux?
A
Torque remains same B
Torque doubles C
Torque halves D
Torque becomes zero
Analysis & Theory
Torque is directly proportional to Iₐ. Doubling Iₐ doubles the torque.
If flux (Φ) in a DC motor is reduced by half, what happens to the torque for the same armature current?
A
Torque becomes double B
Torque becomes half C
Torque remains the same D
Torque becomes zero
Analysis & Theory
Since torque is proportional to Φ, reducing flux by half reduces torque by half.
Which of the following factors affects the torque developed in a DC motor?
A
Armature resistance B
Back EMF C
Flux and armature current D
Commutator type
Analysis & Theory
Torque is a function of both magnetic flux and armature current.
What is the unit of torque in the SI system?
A
Newton B
Watt C
Newton-meter D
Joule
Analysis & Theory
Torque is measured in Newton-meters (N·m) in the SI unit system.
Torque in a DC motor is zero when:
A
Flux is zero B
Speed is zero C
Voltage is maximum D
Armature resistance is zero
Analysis & Theory
If flux is zero, torque becomes zero because T ∝ Φ × Iₐ.
Which motor characteristic curve represents the torque equation in DC motors?
A
Torque vs Flux B
Torque vs Speed C
Torque vs Armature current D
Torque vs Voltage
Analysis & Theory
Torque is directly proportional to armature current when flux is constant.
For a DC shunt motor, under constant voltage, how can torque be controlled?
A
Changing armature current B
Changing series field resistance C
Changing supply frequency D
Using a capacitor
Analysis & Theory
In a DC shunt motor, torque is primarily controlled by varying armature current.
In which type of DC motor does torque increase rapidly with armature current?
A
Shunt motor B
Series motor C
Compound motor D
Separately excited motor
Analysis & Theory
In a DC series motor, both Φ and Iₐ increase, resulting in torque ∝ Iₐ².