Question

Nature of efficiency curve of DC machine is _________________

(a) First decreases then increases

(b) First constant then decreases

(c) First constant then increases

(d) First increases then decreases

I got this question in an interview for internship.

My question is from Efficiency of DC Machine- 2 in section Efficiency and Testing of DC Machines

Answer 1

Correct option is (d) First increases then decreases

The explanation: The efficiency of a DC machine is different at different values of power output. As the output increases, the efficiency increases till it reaches to a maximum value. As the output is further increased, the efficiency starts decreasing slowly.