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GATE 2023 IN – Question 12

Sensors and Industrial Instrumentation · Resistive capacitive and inductive sensors · 1 mark · Multiple choice

Inductance of a coil is measured as 10 mH, using an LCR meter, when no other objects are present near the coil. The LCR meter uses a sinusoidal excitation at 10 kHz. If a pure copper sheet is brought near the coil, the same LCR meter will read____________.

  1. less than 10 mH
  2. 10 mH
  3. more than 10 mH
  4. less than 10 mH initially and then stabilizes to more than 10 mH

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Show answer and explanation

Correct answer: (A) less than 10 mH

Explanation

The alternating field induces eddy currents in copper. By Lenz’s law their opposing field reduces the coil flux linkage per unit current. The effective inductance falls below 10 mH, so **A**. Copper does not provide a high-permeability core.