Question

γ is given as 1.585. Resistance at maximum allowable current is given equal to 4 Ω, what is the 5^th step resistance?

(a) 0.235

(b) 0.370

(c) 1.476

(d) 2

I got this question at a job interview.

I'm obligated to ask this question of Starting of DC Motors topic in chapter DC Motors of DC Machines

Answer 1

Right option is (a) 0.235

Easiest explanation: γ is given as 1.585. So γ^-1 is equal to 0.631. R^1 is provided and it is equal to 4 Ω.

r^1= (1-0.631) * 4 = 1.476 Ω

 r^2= 1.476*0.631= 0.931 Ω, similarly calculating till r^5= 0.235 Ω.