Why the displacement current I_D is always zero in an open surface that is perpendicular to a straight wire whose radius is a?

Question

anonymous · Answer

Displacement current only comes into picture, when there is a changing electric flux!

anonymous · Answer

Don't think so!

anonymous · Answer

it is.. you see.. when a capacitor is charging, electric field is increasing and hence there is a changing electric flux.. which gives rise to a magnetic field.. 

just like how changing magnetic flux, gives rise to an electric field!

anonymous · Answer

Do we have a capacitor here in the example?? There is only a straight wire that contains a constant current I. I know quite the answer and want you to use the Gauss' law though.

anonymous · Answer

exactly.. there is a constant current, due to a constant pd, due to a constant field, due to a constant flux, and hence no displacement current :P

anonymous · Answer

Here's a better answer:|dw:1388665465230:dw|