How to Calculate Magnetic Field Strength Between Parallel Wires

[Kawakaze]

Hi everyone, long time lurker, first time poster. Can someone please clear this up for me? Two wires running parallel to each other. I think its just an algebraic addition of the usual

B(r)=u_0i/2pir

but instead of r, we are using D and d

aslso i apologise for my formulae, if someone could point me to the tex thread ill redo them

Homework Statement

By summing the magnetic field due to currents of magnitude i flowing in both the wires in the senses you found in part (c), show that, on the line joining the two wires, the magnetic field strength is given by =

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Homework Equations

B(r)=u_0i/2pir

The Attempt at a Solution

B=(u_0i/2piD)+(u_0i/2pid)

which i get to be

B=(u_0i)/pi(D^2-d^2)

the question says it should be

B=(u_0iD)/pi(D^2-d^2)

Where is that extra D on the numerator from?

Thanks

 

[kuruman]

We can't help you unless you post the entire problem as stated. What are the "senses you found in part (c)"? What do parts (a) and (b) ask? Guessing at what might be asked does not help us help you.

 

[Kawakaze]

Parts a and b have no bearing on the question. This is just an algebra question. I found out where i went wrong. Just bad practice! =/

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