from matplotlib.pyplot import *
from math import sqrt
from numpy import linspace

fig = figure(figsize=(4,4))
ax1 = fig.add_subplot(111)
ax1.grid(True)

A = 1e-4	# cathode are = 1 cm^2
d = 1e-2	# cathode-anode distance = 1cm
Va = linspace(0,300,100)
e = 1.6e-19		# electronic charge
m = 9.11e-31	# electronic mass
e0 = 8.85e-12	# permitivitty of free space

def childLaw(V):
	return 4.*e0*sqrt(4.*e/m)*A*V**1.5/(d**2*9.)

Ia = childLaw(Va)
ax1.plot(Va,Ia)
ax1.grid(True)

ax1.set_xlabel(r"$V_a$")
ax1.set_ylabel(r"$I_a$")

#fig.show()
fig.savefig("ChildLangmuirLawGraph1.svg",bbox_inches="tight",\
	pad_inches=.15)