File:VFPt magnet B currents.svg
Original file (SVG file, nominally 400 × 300 pixels, file size: 35 KB)
Captions
Summary
[edit]DescriptionVFPt magnet B currents.svg |
English: Magnetic B-field inside and outside of a cylindrical bar magnet. The field is accurately computed with a magnetic current model, where atomic currents add up to an effective current around the magnet (dot symbols for current out of the image plane, cross symbols for current into image plane). Discrete field lines are drawn. |
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Date | |||
Source | Own work | ||
Author | Geek3 | ||
Other versions | without electric current symbols | ||
SVG development InfoField | This plot was created with VectorFieldPlot.
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Source code InfoField | Python code# paste this code at the end of VectorFieldPlot 1.4
import scipy.optimize as op
M = 1.0 # magnetic moment
r = 0.65; l = 1.2
n = 10
fieldB = Field({'coils':[[0, 0, 0, r, l, M/(r**2*pi)]]})
fieldH = Field({'charged_discs':[[-l, -r, -l, r, -0.5*M/l],
[ l, -r, l, r, 0.5*M/l]]})
inside = lambda p: -min(1-fabs(p[0]/l), 1-fabs(p[1]/r))
outside = lambda p: min(1-fabs(p[0]/l), 1-fabs(p[1]/r))
for field in ['B', 'H']:
fname = 'VFPt_magnet_' + field + {'H':'_charges', 'B':'_currents'}[field]
doc = FieldplotDocument(fname, width=400, height=300, commons=True)
for i in range(n):
r_rel = 2 * (0.5 + i) / n - 1
y0 = r * (r_rel + 0.16 * (r_rel - r_rel**3))
p0 = sc.array([l, y0])
line1 = FieldLine(fieldB, p0*(1+1e-9), directions='forward',
maxr=1e4, maxn=1e4, stop_funcs=2*[outside])
doc.draw_line(line1, arrows_style={})
# B-field inside magnet
line2 = FieldLine(fieldB, p0*(1-1e-9), directions='backward',
stop_funcs=2*[inside])
if field == 'B':
doc.draw_line(line2, arrows_style={})
# H-field inside magnet
line3 = FieldLine(fieldH, p0*(1-1e-9), directions='forward',
stop_funcs=2*[inside])
if field == 'H':
doc.draw_line(line3, arrows_style={
'min_arrows':0, 'dist':0.6, 'max_arrows':2})
p1 = line3.nodes[-1]['p'] # where lines leave the magnet on the side
if fabs(p1[1]) >= r * (1-1e-8):
p1[1] = copysign(max(r, fabs(p1[1])), p1[1])
line4 = FieldLine(fieldH, p1, directions='forward',
stop_funcs=2*[outside])
doc.draw_line(line4, arrows_style={'max_arrows':2})
p2 = line4.nodes[-1]['p'] # where lines re-enter the magnet
line5 = FieldLine(fieldH, p2, directions='forward',
stop_funcs=2*[inside])
if field == 'H':
doc.draw_line(line5, arrows_style={
'min_arrows':0, 'dist':0.6, 'max_arrows':2})
line6 = FieldLine(fieldB, p1*(1-1e-9), directions='backward',
stop_funcs=2*[inside])
if field == 'B':
doc.draw_line(line6, arrows_style={})
doc.draw_magnets(fieldB)
if field == 'H':
m = 8
mon = []
for i in range(m):
mon.append([-l, r * ((i+0.5)/m*2-1), -1])
mon.append([l, r * ((i+0.5)/m*2-1), 1])
fieldCharges = Field({'monopoles':mon})
doc.draw_charges(fieldCharges, scale='{:.8f}'.format(r/m/(15./doc.unit)))
else:
m = 15
rings = []
for i in range(m):
rings.append([l * ((i+0.5)/m*2-1), 0, 0, r, 1])
fieldRings = Field({'ringcurrents':rings})
doc.draw_currents(fieldRings, scale='{:.8f}'.format(l/m/(15./doc.unit)))
# postprocessing: strip text and add opacity
for el in doc.svg.iter():
if el.tag.endswith('g'):
if el.get('id') != None and 'magnet' in el.get('id'):
el.set('opacity', '0.4')
if el.tag.endswith('text'):
el.getparent().remove(el)
if el.tag.endswith('circle'):
style = el.get('style')
if style != None:
el.set('style', style.replace('#0000ff', '#00cc00'))
doc.write()
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Licensing
[edit]- You are free:
- to share – to copy, distribute and transmit the work
- to remix – to adapt the work
- Under the following conditions:
- attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
- share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.
File history
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Date/Time | Thumbnail | Dimensions | User | Comment | |
---|---|---|---|---|---|
current | 20:00, 7 May 2017 | 400 × 300 (35 KB) | Geek3 (talk | contribs) | User created page with UploadWizard |
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Metadata
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Short title | VFPt_magnet_B_currents |
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Image title | VFPt_magnet_B_currents
created with VectorFieldPlot 1.4 http://commons.wikimedia.org/wiki/User:Geek3/VectorFieldPlot about: http://commons.wikimedia.org/wiki/File:VFPt_magnet_B_currents.svg rights: Creative Commons Attribution ShareAlike 4.0 |
Width | 400 |
Height | 300 |