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

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SUMMARY

The discussion focuses on calculating the magnetic field at point P on the y-axis due to two current-carrying wires positioned along the x and z axes. The magnetic field from the x-axis wire, with a current of 30A at a distance of 2.0m, is calculated to be 3µT, while the magnetic field from the z-axis wire, with a current of 40A, is 4µT. The resultant magnetic field is incorrectly stated as 1µT, while the correct value should be 5µT, indicating a misunderstanding of vector addition due to the non-parallel nature of the fields. The discussion emphasizes the importance of accurately determining the direction of the magnetic fields based on the right-hand rule.

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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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