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In the four regions, I, II, III and IV, the electric fields are described as : Region I : \(E _{ x }= E _0 \sin ( kz -\o…

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In the four regions, I, II, III and IV, the electric fields are described as :

Region I : \(E _{ x }= E _0 \sin ( kz -\omega t )\)
Region II : \(E _{ x }= E _0\)
Region III : \(E _{ x }= E _0 \sin kz\)
Region IV : \(E _{ x }= E _0 \cos kz\)
The displacement current will exist in the region :

a

I

b

IV

c

II

d

III

✓ Correct answer: a)

I

Explanation

Displacement current density,

\({J}_{d}={\epsilon }_{0}\frac{dE}{dt}\)

Region I : \({E}_{x}={E}_{0}\sin \left(kz-\omega t\right)\\ \frac{d{E}_{x}}{dt}=-\omega {E}_{0}\cos (kz-\omega t)\\ {J}_{d}=-{\epsilon }_{0}\omega {E}_{0}\cos (kz-\omega t)\)

Region II : \({E}_{x}={E}_{0}\Rightarrow \frac{d{E}_{x}}{dt}=0\\ {J}_{d}=0\)

Region III : \({E}_{x}={E}_{0}\sin (kz)\\ \frac{dE}{dt}=0\Rightarrow {J}_{d}=0\)

Region IV : \({E}_{x}={E}_{0}\cos (kz)\\ \frac{dE}{dt}=0\Rightarrow {J}_{d}=0\)

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