Question

The slope of the V-I curve is 78°. Calculate the value of resistance. Assume the relationship between voltage and current is a straight line.

(a) 4.732 Ω

(b) 4.608 Ω

(c) 4.543 Ω

(d) 4.648 Ω

I have been asked this question during an interview.

This interesting question is from Modified Speed Torque Characteristics of DC Shunt Motors topic in chapter Characteristics of DC & AC Motors of Electric Drives

Answer 1

Right option is (a) 4.732 Ω

The explanation: The slope of the V-I curve is resistance. The slope given is 78° so R=tan(78°)=4.732 Ω. The slope of the I-V curve is reciprocal of resistance.