Question

To construct a solenoid, you wrap insulated wire uniformly around a plastic tube 12 cm in diameter and 45 cm in length. You would like a 2.0-A current to produce a 2.1-kG magnetic field inside your solenoid. What is the total length of wire you will need to meet these specifications? Any help is greatly appreciated. Please let me know how you did this and not just the answer so I can learn how to solve it.

Answer 1

x=0.45 m, D=0.12 m,
I= 2 A, B=2.1 kG=2100G= 0.21 T
μ₀=4π•10⁻⁷ H/m
B=μ₀nI = μ₀NI/x
N=Bx/ μ₀I
The length of the wire
L=N•πD= Bx πD / μ₀I=
=0.21•0.45•π•0.12/4π•10⁻⁷•2=14175 m