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1)Is the sum of conduction and displacement current constant? 2)And is it possible to get a displacement current in a DC circuit?

Is it right to say: Displacement current only exists when there is a varying electric field,which is possible only in AC.Hence it would be absent in dc

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    $\begingroup$ The displacement current in a capacitor (that is what you mean, right?) is the same as the current trough the leads of the capacitor (which is the conduction current in your question?). A displacement current, by definition, requires a time varying electric field or polarization. $\endgroup$ – CuriousOne Feb 25 '16 at 11:01
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1) When you say constant, do you mean constant over time? The answer to that is no (if you have a time-varying current or voltage source, then you'll have time-varying currents). If you mean, the sum of conduction and displacement current is the same everywhere within a branch of a circuit, this is true by Kirchoff's current law.

2) Yes, a time varying field is required, but this can happen in a DC circuit across capacitors while they are charging up.

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  • $\begingroup$ Is there any difference between the displacement current produced by DC and ac circuit? $\endgroup$ – Snowy Feb 25 '16 at 12:15
  • $\begingroup$ Hmmm... the only difference I see is... in a DC circuit there's no displacement current across the non-capacitor elements. In an AC circuit, you'll have displacement current across the non-capacitor elements, but they will be negligible compared to the conduction current, unless you get to very high frequencies. The better the conductor, the higher the frequency when displacement current catches up to conduction current. $\endgroup$ – Ameet Sharma Feb 25 '16 at 12:43

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