Question

The inductance of a certain moving- iron ammeter is expressed as L = 10 + 3θ – \frac{θ^2}{4} μH, where θ is the deflection in radian from the zero position. The control spring torque is 25 × 10^-6 Nm/rad. If the meter is carrying a current of 5 A, the deflection is ____________ (a) 2.4 (b) 2.0 (c) 1.2 (d) 1.0 This question was posed to me by my college director while I was bunking the class. This intriguing question comes from Advanced Problems on Magnetically Coupled Circuits topic in chapter 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 choice is (c) 1.2 To explain: At equilibrium, Kθ = \frac{1}{2} I^2 \frac{dL}{dθ} (25 × 10^-6) θ = \frac{1}{2} I^2 (3 – \frac{θ}{2}) × 10^{-6} ∴ 2 θ + \frac{θ}{2} = 3 Or, θ = 1.2.