Question

What will be the value of Req in the following Circuit?

(a) 11.86 ohm

(b) 10 ohm

(c) 25 ohm

(d) 11.18 ohm

I got this question by my school teacher while I was bunking the class.

My question is from Basic Concepts in section EDC Overview of Electronic Devices & Circuits

Answer 1

Correct choice is (d) 11.18 ohm

The explanation: We infer from the given diagram that the same pattern is followed after every 10ohm resistor. The infinite pattern in parallel as a whole is considered as to be Rx.

Thus, Rx = R + (R||Rx)

Solving for Rx, we get Rx = 1.62R, where R=10ohm.

So we have Rx = (1.62ohm)*(10ohm), which gives Rx=16.2ohm

Therefore, Req = 5 + (10||16.2)

=> 5 + [(10*16.2)/(10+16.2)]

=> Req = 5 + (162/26.2) which gives Req=11.18 ohm.