Physics GRE GR 1777

5. Electrodynamics (Maxwell’s Equations)

Solution) In Maxwell’s equations, Ampère’s law (with Maxwell’s correction) is

.

We can write this equation as

,

where is the current (the electric displacement current). And is change of electric fields with respect to the time (rate of change of the electric flux).

If we assume that , and the current flows through a surface *S*, then we can clearly see that the electric displacement current through *S* is proportional to the rate of change of the electric flux through *S*.

Therefore, the answer is (E).

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Another (and better) solution)

The definition of electric displacement current is

.

If you know this definition, the problem would be solved more easily.

Reference: https://en.wikipedia.org/wiki/Displacement_current

# GRE GR 1777, Problem 005 Solution

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