6. B] With usual notations, develop the torque equation of the D.C motor.
Answer:
The turning or twisting force about an axis is called torque.
Consider a wheel of radius R meters acted upon by a circumferential force F newtons.
The wheel is rotating at a speed of N rpm then its angular speed is
so work done in one revolution is
W= F x distance travelled in one revolution = F x 2 π R
Therefore, P = T x ω watts
Let Ta be the gross torque developed by the armature of the motor. It is also called armature torque.
The gross mechanical power developed in the armature is EbIa .
So if the speed of the motor is N rpm, then
Power in armature = Armature torque x ω
