code: ################################################################################
  #
  #  BFIELD
  #
  #   Simple example of plot of the magnitude of the magnetic field
  #   produced by a current loop, using its Cartesian components
  #
  #
  ################################################################################
  
  import numpy as np
  import bfield
  import matplotlib.pyplot as plt
  
  # Current Loop
  Ra = 0.05
  I0 = 100.
  Nturns = 1
  Center = np.array([0,0,0])
  Angles = np.array([90,0,0]) * np.pi/180.0
  
  # X,Y Grid
  X = np.linspace(-0.1, 0.1, 50 )
  Y = np.linspace(-0.1, 0.1, 50 )
  
  # B-field magnitude
  Bnorm = np.zeros((X.size,Y.size))
  for i in range(0,X.size):
    for j in range(0,Y.size):
      Point = np.array([ X[i], Y[j], 0.0 ])
      Bx,By,Bz = bfield.loopxyz(Ra,I0,Nturns,Center,Angles,Point)
      Bnorm[i][j] = np.sqrt(Bx*Bx + By*By + Bz*Bz)
  
  plt.figure(1)
  XX,YY = np.meshgrid(X,Y)
  plt.contourf(np.transpose(XX),np.transpose(YY),Bnorm,30)
  plt.colorbar()
  plt.xlabel('X [m]')
  plt.ylabel('Y [m]')
  plt.title('B-field magnitude [T] of a Current Loop')
  plt.savefig('ex03_plot_loopxyz_magnitude.png',dpi=150)
  plt.show()
  
apis: numpy.sqrt numpy.transpose numpy.zeros matplotlib.pyplot.figure matplotlib.pyplot.savefig matplotlib.pyplot.title matplotlib.pyplot.show matplotlib.pyplot.ylabel numpy.array matplotlib.pyplot.colorbar numpy.meshgrid numpy.linspace matplotlib.pyplot.xlabel