Question

In the hopkinson’s test on two DC machines. Machine A has field current of 1.4A and B has field current of 1.3A. Which machine acts as motor?

(a) B

(b) A

(c) A, B

(d) None of the mentioned

This question was posed to me by my school teacher while I was bunking the class.

I'd like to ask this question from Efficiency and Testing of DC Machines topic in chapter DC Machines of Electrical Machines

Answer 1

Correct answer is (a) B

To explain I would say: Ea/Eb = 1.4/1.3

             Ea = 1.077 Eb > Eb

             So, the machine will act as motor.