Final answer:
To find the field current and the armature current of a 120 V DC shunt motor, Ohm's Law is used considering the resistances provided. The field current is 1 A, and the armature current is 40 A. Without the back emf, the developed power and torque cannot be calculated.
Step-by-step explanation:
The question involves a 120 V DC shunt motor that draws a line current of 41 A and has an armature and field resistances of 0.1 Ω and 120 Ω, respectively. The speed of the motor is given as 200 rad/sec.
- Field current (If): This can be calculated using Ohm's Law (V=IR), where V is the supply voltage and Rf is the field resistance. The 120 V supply is across the field winding, so If = V / Rf = 120 V / 120 Ω = 1 A.
- Armature current (Ia): The armature current can be found by subtracting the field current from the total line current. Ia = Itotal - If = 41 A - 1 A = 40 A.
- Developed power (P): This is the power developed in the armature and can be calculated using the formula P = Ia * Ea, where Ea is the back electromotive force (emf). Since we are not given Ea, we cannot directly calculate the developed power without further information.
- Developed torque (T): Torque can be calculated using the formula T = P / ω, where P is the power (which we cannot calculate without Ea) and ω is the angular velocity. Again, without Ea, we are unable to calculate the torque directly.
Due to the lack of information regarding back emf (Ea), parts (c) and (d) cannot be resolved without making assumptions or having additional data.