Does a straight non-time-dependent E field create a circular B field?

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Discussion Overview

The discussion centers around the relationship between electric fields (E fields) and magnetic fields (B fields), particularly whether a straight, non-time-dependent E field can create a circular B field. The scope includes theoretical considerations from electrodynamics and relativity.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant suggests that a non-time-dependent E field does create a circular B field based on Ampere's law, questioning whether a current in a wire is actually a time-dependent E field.
  • Another participant asserts that in the context of the current in a wire, it is the current itself that generates the B field, not an E field.
  • A third participant introduces the idea that relativity indicates there is no separation between E and B fields, proposing that in different reference frames, a pure electrostatic E field can correspond to both E and B fields in a moving frame.
  • One participant acknowledges the relativity point but maintains that the original question regarding the current in a wire being a time-dependent E field is answered negatively.
  • A later reply reiterates that while an E field may have existed initially for the current to be present, it does not currently exist in the scenario being discussed, emphasizing that the B field is attributed to the current itself.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between E fields and B fields, with no consensus reached on whether a non-time-dependent E field can create a circular B field or if the current in a wire can be considered a time-dependent E field.

Contextual Notes

There are unresolved assumptions regarding the definitions of electric and magnetic fields, as well as the implications of relativity on their relationship. The discussion does not clarify the conditions under which these fields interact or the specific scenarios being considered.

zheng89120
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I was under the impression that it does, you know from Ampere's law. But today, my professor told me that Electric and Magnetic fields are very similar (although I can't imagine they are exactly the same, since there are no magnetic monopoles), THAT a non-time dependent E field does not create a circular B field. Does this mean that a current in a wire is actually a time-dependent E field?

Thanks.

PS. the course that this was from was Relativistic Electrodynamics.
 
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No, in this example there is no E field. It's the current in the wire that creates the B field.
 
Nevertheless, relativity tells us that there is not a separated E and B field, but only one electromagnetic field. If you have in one frame of reference a pure electrostatic E field in another frame of reference, moving relative to the first, you have both an E and a B field. Both fields together make up the electromagnetic field. (E,B) are the components of an antisymmetric 2nd-rank tensor in Minkowski space.
 
That's quite true, but has nothing to do with the present thread. The question was, "is the current in a wire actually a time-dependent E field?" and the answer is no.
 
Bill_K said:
No, in this example there is no E field. It's the current in the wire that creates the B field.

Actually, there was at some moment an E field (for the current to be there in the first place) but no longer there is, whether one decides to attribute the B field to this E field change or to the actual current it makes no difference at all.
 

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