Question

The slope of the V-I curve is 39.1°. Calculate the value of resistance. Assume the relationship between voltage and current is a straight line.

(a) .81 Ω

(b) .36 Ω

(c) .75 Ω

(d) .84 Ω

I have been asked this question at a job interview.

Enquiry is from Speed Control of Shunt or Separately Excited Motors topic in section Speed Control of Direct Current Motors & Induction Motors of Electric Drives

Answer 1

Right choice is (a) .81 Ω

Explanation: The slope of the V-I curve is resistance. The slope given is 39.1° so R=tan(39.1°)=.81 Ω. The slope of the I-V curve is reciprocal of resistance.