Physics Question about magnetic field. Please Help!! In great need!!?

Question

What current is required in the windings of a long solenoid that has 900 turns uniformly distributed over a length of 0.380 m in order to produce a magnetic field of magnitude 1.00 10-4 T at the center of the solenoid? Please put answer in mA.

Answer 1

I=?
N= 900
L=0.38 m
B=1x10^-4 T

B=k' N 4πI/L

I= BL/k' N 4π
I=[(1x10^-4 T)(0.38 m)]/[(10^-7N/A²)(900)(4*3.1416)]
I=0.03359 A
I=33.59 mA

Answer 2

A solenoid is really a very nice device when it comes to magnetic fields. The fields created are nearly uniform inside the solenoid. Magnetic fields are created by moving charges (currents). In this case, we model a moving charge through several loops of wire. The number of loops per unit length and the constant mu with a subscript 0 is need to figure this out.

If I remember right (you should make sure I am not wrong as I am going from memory here):

B = mu * n * I

where B is the magnetic field strength
mu is the constant mu subscript 0 (mu-naught or mu-zero)
n is the turns per unit length
I is the current

Solve for current:

I = B /( mu * n)

Plug in the numbers and calculate. The previous answerers are doing the same thing. I believe that Welder's answer is correct. The first answer is ten times too big. 0.0335 amps = 33.5 mA.

Good luck.

Answer 3

Magnetic field (B) is current (I) times the number of windings (N) divided by length (L) all times a constant. The constant is the Greek letter "mu" with a subscript of 0, and whose value is 4*pi*10^-07 T*m/A.

.0001=(I)*4*pi*10^-07*900/.38
3.8*10^-05=(I)*4*pi*10^-07*900
.4222=(I)*4*pi
I=.0336 Amps.
To get mA, multiply by 1000=336mA.