What Is the Magnetic Field at Point P on the Y-Axis?

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Homework Help Overview

The problem involves calculating the magnetic field at a point P on the y-axis due to currents in wires positioned along the x-axis and z-axis. Participants are exploring the contributions of these currents to the magnetic field at point P, with specific values for current and distance provided.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the calculations for the magnetic fields generated by the currents, questioning the directions of these fields and their resultant vector nature. There is uncertainty regarding the correct interpretation of the magnetic field directions based on the setup.

Discussion Status

The discussion is ongoing, with participants clarifying assumptions about the setup and the directions of the magnetic fields. Some guidance has been offered regarding the interpretation of the diagram, but there is no explicit consensus on the correct direction of the magnetic fields at point P.

Contextual Notes

Participants are working under the assumption that the paper is in the xy-plane, which influences their understanding of the magnetic field directions. There is also a noted discrepancy between calculated and expected results, prompting further exploration of the problem.

Physicslearner500039
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Homework Statement
One long wire lies along an x axis and carries a current of 30A in the positive x direction. A second long wire is perpendicular to the xy plane, passes through the point (0,4.0 m, 0), and carries a current of 40 A in the positive z direction. What is the magnitude of the resulting magnetic field at the point (0,2.0 m, 0)?
Relevant Equations
Magnetic field due to long wire (μ0*i)/(2*π*r)
Prob1.JPG

The problem is as above, My attempt is as below but there is lot of effort in terms of imagining and not very confident,
Required the magnetic field on the y-axis let us say point P.
The magnetic field due to the x-axis wire is out of the paper at P with the values as R=2.0m, i =30A.
B1 = (μ0*i)/(2*π*r) = (4*π*(10^-7)* 30)/(2*π*2) = 3uT,
For the Z axis wire the magnetic field is again into the paper at P with the values as R=2.0m, i = 40A
B2 = (μ0*i)/(2*π*r) = (4*π*(10^-7)* 40)/(2*π*2) = 4uT. The resultant is 1uT. The answer does not seem to match it is 5uT. Please advise.
 
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The two fields are not parallel to each other.
 
Last edited:
Physicslearner500039 said:
For the Z axis wire the magnetic field is again into the paper at P
Really?
 
Really?
Yes it is coming out of the paper.
 
Physicslearner500039 said:
For the Z axis wire the magnetic field is again into the paper at P
How did you conclude this?

(I assume the paper is in the xy-plane, i.e. perpendicular to the z-axis at z = 0.)
 
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Yes
 
Physicslearner500039 said:
Yes
Good. From the diagram, what is the direction of the magnetic field at the red dot due to current ##I_2##?
 
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Yes i think it is in positive X direction. Am i correct?
 
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Yes :oldsmile:
 
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