# Chapter 8 : Magnetic properties and conductivity¶

## Example 8.3 Page No : 354¶

In :
import math

# Given
Mat = 55.85*10**-3          # in Kg/mol
NA = 6.022*10**23           # in mol**-1
p = 7.86*10**3              # in kg/m3
Msat = 1.75*10**6           # in A/m
# funcprot(0)
beta = 9.27*10**-24         # in J/tesla

# Calculations and Results
n_at = p*NA/Mat
x = Msat/(n_at*beta)
print("In the solid each Fe atom contributes only {0:.4f} bohr magneton".format(x))

In the solid each Fe atom contributes only 2.2275 bohr magneton


## Example 8.5 Page No : 358¶

In :
import math

# Given
u_o = 4*math.pi*10**-7      # in H/m
u_ri = 2*10**3
N = 200.0                   # no. of turns
d = 0.005                   # in m
D = 2.5*10**-2              # in m

# Calculations and Results
A = math.pi*(d**2)/4
l = math.pi*D
L = u_ri*u_o*N**2*A/l
print("Approximate inductance of the coil in Henry is {0:.4f}".format(L))

Approximate inductance of the coil in Henry is 0.0251


## Example 8.7 Page No : 359¶

In :
import math

# Given
N = 500.0                 # no.of turns
B = 5.0                   # in Tesla
l = 1.0                   # in m
r = 10**-3              # in m
uo = 4*math.pi*10**-7   # in H/m
d = 10*10**-2           # in m

# Calculations and Results
I = (B*l)/(uo*N)
print("current in Amperes is {0:.4f}".format(I))
E_vol = B**2/(2*uo)
v = math.pi*l*d**2/4.0
E = E_vol*v
print("Energy stored in the solenoid in joules is {0:.4f}".format(E))

current in Amperes is 7957.7472
Energy stored in the solenoid in joules is 78125.0000