Magnetic field of a straight current-carrying conductor

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Homework Help Overview

The discussion revolves around the magnetic field generated by a straight current-carrying conductor when a sine wave current is applied. The original poster is exploring how the magnetic field differs from that produced by a direct current, referencing a known formula for the magnetic field due to a DC current.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to modify the known magnetic field formula for a DC current to accommodate a sine wave current. Participants question the implications of frequency on the magnetic field and discuss the potential phase shift between the current and the magnetic field at a distance from the wire.

Discussion Status

Participants are actively engaging with the original poster's inquiry, with some offering insights about the conditions under which the sine wave current can be analyzed. There is an ongoing exploration of the relationship between the current and the resulting magnetic field, particularly regarding phase shifts and the effects of high-frequency currents.

Contextual Notes

There is a mention of the need for a diagram to clarify the variables involved, specifically the definitions of distance x and a. Additionally, some participants express skepticism about the realism of applying high-frequency currents without considering the behavior of charges in the conductor.

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Homework Statement
To find the magnetic field in a straight current carrying conductor due to sine wave at a distance x on its perpendicular bisector.
Relevant Equations
##B = \frac {\mu_0 I 2a} {4\pi x\sqrt{x^2 + a^2}}##
It is not a direct home work problem, i was thinking if a sine wave current passes through the straight current carrying conductor, what will be the magnetic field. For the DC current I know the formula as below.
##B = \frac {\mu_0 I 2a} {4\pi x\sqrt{x^2 + a^2}}##
Let the current be ##I = I_0\sin(\omega t)## then will the magnetic field be
##B = \frac {\mu_0 I_0\sin(\omega t) 2a} {4\pi x\sqrt{x^2 + a^2}}##
 
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PhysicsTest said:
Homework Statement:: To find the magnetic field in a straight current carrying conductor due to sine wave at a distance x on its perpendicular bisector.
Relevant Equations:: ##B = \frac {\mu_0 I 2a} {4\pi x\sqrt{x^2 + a^2}}##

It is not a direct home work problem, i was thinking if a sine wave current passes through the straight current carrying conductor, what will be the magnetic field. For the DC current I know the formula as below.
##B = \frac {\mu_0 I 2a} {4\pi x\sqrt{x^2 + a^2}}##
Let the current be ##I = I_0\sin(\omega t)## then will the magnetic field be
##B = \frac {\mu_0 I_0\sin(\omega t) 2a} {4\pi x\sqrt{x^2 + a^2}}##
Could you attach a diagram showing what ##x## and ##a## are in your question?

And yes, if the wavelength of the B-field sinusoid (propagating at c) is long compared to how close to the wire you want your solution to work, then you just multiply by the sinusoid function itself. If that condition does not hold, then there will be a phase shift between the driven current in the wire and the B-field sensed away from the wire. Does that make sense?

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magcur.html

1601159562993.png
 
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The diagram is
1601186189605.png

berkeman said:
If that condition does not hold, then there will be a phase shift between the driven current in the wire and the B-field sensed away from the wire.
How do I calculate the phase shift? Can you provide a hint, I will attempt.
 
It is not very realistic to let the current vary with such a high frequency that the propagation to point P is influenced, without considering what happens to the charge in the conductor.

Perhaps you want to look at the phenomena associated with a radiating dipole ?
 
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