The GATE Grind

GATE 2026 EC – Question 28

Electromagnetics · Plane Waves and Properties · 1 mark · Multiple select

Which option(s) represents/ represent the dielectric loss tangent of a substrate?

  1. Ratio of the real to imaginary parts of the total displacement current
  2. $(\omega\epsilon''+\sigma)/(\omega\epsilon')$
  3. Ratio of the electric susceptibility to permittivity
  4. Ratio of the polarization vector $\vec P$ to the displacement vector $\vec D$

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Correct answer: (A) Ratio of the real to imaginary parts of the total displacement current; (B) $(\omega\epsilon''+\sigma)/(\omega\epsilon')$

Explanation

The total current density is $J=(\omega\epsilon''+\sigma)E+j\omega\epsilon' E$. So $\tan\delta=(\omega\epsilon''+\sigma)/(\omega\epsilon')$, the ratio of the real (loss) part to the imaginary part. Options C and D are not loss tangent.