# Did I find the correct ratio in this magnetic field question?

#### HazyMan

Homework Statement
A current carrying coil has a spiral amount N1, length L and a current of I1 flows through it. A current of I2=2I1 flows through a cyclic current carrying wire, which has the coil's axis start as it's centre, has a radius of r=L/λ and is parallel to it. Find the spiral ratio N1/N2 where the magnitude B is equal to 0.
NOTE: Kμ is a constant equal to 10^-7
Homework Equations
B1=Κμ4π(N1/L)I1 and B2=Κμ(4πI1/L)λN2
I used the two equations i listed by using [TEX]B1=B2[/TEX] and by doing that i ended up finding that [TEX]N1/N2=λ[/TEX].
However i am not sure if that's the correct answer as λ is just a variable and not an actual number. Do you think it has to be an actual number or is it not really necessary?

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#### Delta2

Homework Helper
Gold Member
I am not sure I understand the problem setup entirely (you dont tell us for example what $N_2$ is and also a scheme would help enormously, if you have a picture of it, use the upload image link to post it here) but I think the correct answer should be $2\lambda$ since the current in the second coil is two times the current of the first coil.

"Did I find the correct ratio in this magnetic field question?"

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