# mathematical expression used to calculate magnetic field of straight conductor

Discussion in 'Homework Help' started by PG1995, Sep 5, 2012.

1. ### PG1995 Thread Starter Well-Known Member

Apr 15, 2011
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Hi

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Regards
PG

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2. ### nobody0608 New Member

Aug 4, 2012
28
2
Hello.

From my opinion, it might not be able to solve the problem in that way as the r is actually belong to another kind of coordinate system. If I was not mistaken, they use cylindrical coordinate system to solve this equation.

From my understanding,
R axis is represented as the radial distance which fall on the x-y plane of the cartesian coordinate system.
θ axis is represented as the azimuth angle that start measure from positive x-axis.
Z axis in this system is having same definition with cartesian coordinate system.

image from LivePhysics - Coordinate Systems

There is an important statement in the last paragraph regarding to the direction of B.
It means that the direction of the B will keep changing in the x-z plane (in your text book case). This make it become angular case. So the system have to be changed and an angular term have to be assigned for direction of the B.

The equation that included its direction will be given as

So, it's no longer in the cartesian coordinate system.

*p/s: The term of equation above should be in θ, sorry for mistyping. Changed due to the term used in the image from LivePhysics.

Last edited: Sep 6, 2012
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