Question

Determine the current flowing in the ammeter having 1Ω internal resistance connected in series with the 6Ω resistor as shown in the below circuit.

(a) 0.4

(b) 0.45

(c) 0.9

(d) 0.95

The question was posed to me during an interview for a job.

This intriguing question comes from Compensation Theorem in chapter Useful Theorems in Circuit Analysis of Network Theory

Answer 1

Correct option is (b) 0.45

For explanation I would say: Current through 3Ω resistor = 0.55A. So voltage drop across 1Ω resistor = 0.55×1 = 0.55V.

Now the circuit can be modified as

Now current through 6Ω resistor = 0.094A. This current is opposite to the current calculated before. So ammeter reading = (0.55-0.0.94) = 0.45A.