Magnetic field sim

magfieldcurl.py

from __future__ import division
from visual import *
from math import *

PROTON_CHARGE = 100
MU_ZERO = 1.256e-6
VEL = vector(.01, 0, 0)  # m/s
SCALE = 20

observation_points = [vector(x * .01 - .1, .01 * cos(pi/4 * t), .01 * sin(pi/4 * t)) for x in range(20) for t in range(8)]
arrows = [arrow(pos=p, axis=vector(0, 0, 0), color = color.green) for p in observation_points]

particle = sphere(pos=vector(-.1, 0, 0), radius=.005, color = color.red)

def update_arrows(pos):
    """
    updates arrows to reflect the particle being at position pos.
    """
    for a in arrows:
        r = a.pos - pos
        b = MU_ZERO/(4*pi)*PROTON_CHARGE*VEL.cross(r/r.mag)/r.mag**2
        a.axis = SCALE * b

while True:
    rate(100)
    update_arrows(particle.pos)
    particle.pos += VEL * .01
    if particle.pos.x >= .1:
        particle.pos.x = -.1