PHYS 220 — Lab #8 [Solution]
This lab is a two-part sequence that will address certain topics
in electromagnetism. In this part you will numerically integrate
the Biot-Savart law to find the B-field for a solenoid. By doing this
you'll be obtaining
results off-axis, results that cannot be obtained in closed form
analytically. I'll provide you with
a visualization script for your
solution.
The assignment is
due at the beginning of lecture on
Monday, 13 April.
Your solutions should include a code listing
and plots based on my visualization script. HW
#7 will be in support of this lab.
- The solenoid you'll be modeling comprises N turns, height h,
radius 1 and a current 4π/μo flows through it. It
is centered in the x-y plane and it's axis is along the z-axis.
The coil begins at (1,0,h/2) and spirals down to (1,0,-h/2). The
current flows downward in the z-direction.
- For each of the following parameters, find the vector B at
(0,0,0) and (0,0,±h/2). Compare your results with the
theoretical values B = Bz = 4πN/h in the center and B
= Bz = 2πN/h at the ends.
Δθ = π/10 will provide you with sufficient resolution.
- N = 80, h = 2
- N = 100, h = 10
- N = 1000, h = 100
In the table below, I list Bz/Bz,theory for each
of the conditions and locations. Note that as N & h get large, the
solenoid acts more like an ideal one.
|
z = 0 |
z = +h/2 |
z = -h/2 |
| N = 80, h = 2 |
0.7071 |
0.8950 |
0.8939 |
| N = 100, h = 10 |
0.9806 |
0.9975 |
0.9925 |
| N = 1000, h = 100 |
0.9998 |
1.003 |
0.9975 |
- Using N = 150 and h = 2, use
my visualization script to
image the B-field in the x-y and x-z planes.
Your figure should look something like the one below. You'll assess
the results in HW #8.