Question

For the circuit given below, the inductance measured across the terminals 1 and 2 was 15 H with open terminals 3 and 4. It was 30 H when terminals 3 and 4 were short-circuited. Both the inductors are having inductances 2H. The coefficient of coupling is ______________ (a) 1 (b) 0.707 (c) 0.5 (d) Inderminate due to insufficient data This question was addressed to me by my school principal while I was bunking the class. My doubt is from Advanced Problems on Magnetically Coupled Circuits in section Resonance & Magnetically Coupled Circuit of Network Theory Select the correct answer from above options network theory questions and answers, network theory questions pdf, network theory question bank, network theory gate questions and answers pdf, mcq on network theory pdf, gate network theory questions and solutions, network theory mcq Test , ies network theory questions, Network theory Questions for GATE EC Exam, Network Theory MCQ (Multiple Choice Questions)

Answer 1

The correct answer is (d) Inderminate due to insufficient data To elaborate: When 2 coils are connected in series, then effective inductance, LEFF = L1 + L2 ± 2M For this case, LEFF = L1 + L2 – 2M However, L1 + L2 + 2M or L1 + L2 – 2M cannot be determined. Hence, data is insufficient to calculate the value of coupling coefficient (k).