Magnetic field of a wire with current running through it

[Dell]

on an x,y,z axis i have a wire with infinite length placed on the z axis with a current of 2A running through it downwards, in addition i have a magnetic field of 2*10^-7T in the Y+ direction, what is the magnetic firld at
A(1,0,0)
B(0,1,0)
C(-1,0,0)

i know that my field at each point must be the sum of the fields at the points, so it will be 2*10^-7T*Y + the field of the wire,


what equation cani use to find the field of an endless wire??

 

[tiny-tim]

what equation cani use to find the field of an endless wire??

You tell us! …

you'll have to integrate over ds from -∞ to +∞

 

[Dell]

i thought that might be it, using Biot-Savart Law?

dB=μ₀I/(4∏)*dlxr/r³
but since the wire is 90 degrees to r
dB=μ₀I/(4∏)*dl/r²

B=∫μ₀I/(4∏)*dl/r²
B=μ₀I/(4∏r²)*∫dl

but that will give me infinity?

 

[tiny-tim]

??

you haven't included the variation in distance (use Pythagoras)

(oooh … and have a small pi: π )

EDIT: hello Redbelly!

 

[Redbelly98]

The wire is not at 90 degrees to r everywhere:

http://electron9.phys.utk.edu/phys136d/modules/m7/images/dl.gif [Broken]

That being said ... doesn't your textbook discuss the magnetic field of a long straight wire?

 

[Dell]

so would i say r=sqrt(1+L^2) ??

dB=μ0I/(4∏)*dL/(1+L^2)

 

[tiny-tim]

so would i say r=sqrt(1+L^2) ??

dB=μ0I/(4∏)*dL/(1+L^2)

yes, except these are vectors, so you need a cosine in there, don't you?

 

[Redbelly98]

yes, except these are vectors, so you need a cosine in there, don't you?

Or perhaps a sine?

p.s. Hello tiny-tim