A 440 𝑉 dc series motor of negligible resistance and with unsaturated magnetic circuit takes 50 𝐴 when running at a certain speed on a given load. If the load torque varies as the cube of the speed, the resistance necessary to reduce the speed by 50 % will be:
A. 20.5 Ω
B. 24.0 Ω
C. 28.5 Ω
D. 32.0 Ω
Answer:A
A 440 𝑉 dc series motor of negligible resistance and with unsaturated magnetic circuit takes 50 𝐴 when running at a certain speed on a given load. If the load torque varies as the cube of the speed, the resistance necessary to reduce the speed by 50 % will be:
A. 20.5 Ω B. 24.0 Ω C. 28.5 Ω D. 32.0 Ω