Question

When a DC voltage is applied to an inductor, the current through it is found to build up in accordance with I = 20(1-e^-50t). After the lapse of 0.02 s, the voltage is equal to 2 V. What is the value of inductance? (a) 2 mH (b) 5.43 mH (c) 1.54 mH (d) 0.74 mH I had been asked this question by my school principal while I was bunking the class. Asked question is from Problems Involving Dot Conventions 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

Right choice is (b) 5.43 mH The best explanation: VL = L\frac{dI}{dt} Where, I = 20(1-e^-50t) Therefore, VL = L\frac{d 20(1-e^{-50t})}{dt} = L × 20 × 50e^-50t At t = 0.02 s, VL = 2 V ∴ L = \frac{2}{20 × 50 × e^{-50×0.02}} = 5.43 μH.