Question

The series combination of the last elements after replacing 1/s and 1/4Ω with 1/(S+4) is?

(a) (3s+4)/2s(s-4)

(b) (3s-4)/2s(s-4)

(c) (3s+4)/2s(s+4)

(d) (3s-4)/2s(s+4)

The question was posed to me in an interview for job.

Enquiry is from Series and Parallel Combination of Elements topic in portion S-Domain Analysis of Network Theory

Answer 1

Correct answer is (c) (3s+4)/2s(s+4)

To explain: We got the impedance of last two elements in parallel combination as Z1(s) = 1/(s+4) and now the impedance of capacitor is 1/2s. So the series combination of the last elements is Z2(s) = 1/2s+1/(s+4) = (3s+4)/2s(s+4).