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GATE 2014 EE (EE2) – Question 16

Electromagnetic Fields · Inductance, Magnetomotive force, Reluctance, Magnetic circuits, Self and Mutual inductance of simple configurations · 1 mark · Numerical answer

Two identical coupled inductors are in series. The two possible series connections measure 380 µH and 240 µH. Find mutual inductance (µH).

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Correct answer: 35 to 35

Explanation

For identical coils,Laiding=2L+2M=380µH and Lopposing=2L−2M=240µH. Subtract to obtain4M=140µH,so **M=35µH**. Their sum also gives L=155µH,consistent with a coupling coefficient35/155below unity.