In [1]:

```
#pg 267
#calculate the current
# Given data
from math import pi
a = 3;# in cm^2
a = a * 10**-4;# in m^2
d = 20;# in cm
N = 500;
phi = 0.5*10**-3;# in Wb
miu_r = 833.33;
#calculations
miu_o = 4*pi*10**-7;
l = pi*d;# in cm
l = l * 10**-2;# in m
S = l/(miu_o*miu_r*a);# in AT/Wb
# Calculation of the current with the help of flux
# Formula phi = (m*m*f)/S = (N*I)/S;
I = (phi*S)/N;# in A
#results
print "The current in A is",round(I)
```

In [2]:

```
#pg 268
#calculate the reluctance, flux, field strength, coil mmf and permeance
# Given data
from math import pi
N = 300.;
miu_r = 900.;
l = 40.;# in cm
a = 5.;# in cm**2
R = 100.;# in ohm
V = 250.;# in V
#calculations
miu_o = 4*pi*10**-7;
I = V/R;# in A
mmf = N*I;# in AT
print "The coil mmf in AT is",mmf
H = (N*I)/(l*10**-2);# in AT/m
print "The field strength in AT/m is",H
B = miu_o*miu_r*H;# in Wb/m**2
phi = B*a*10**-4;# in Wb
print "Total flux in Wb is",round(phi,5)
S = mmf/phi;# in AT/Wb
print "The reluctance of the ring in AT/Wb is",round(S,2)
# Permeance is recipocal of reluctance
Permeance = 1/S;# in Wb/AT
print '%s %.1e' %("Permeance of the ring in Wb/AT is",Permeance)
```

In [3]:

```
#pg 269
#calculate the amphere turns
# Given data
from math import pi
Ig = 4;# in mm
Ig = Ig * 10**-3;# in m
B = 1.3;# in Wb/m**2
miu_r = 1;
#calculations
miu_o = 4*pi*10**-7;
H = B/(miu_o*miu_r);# in AT/m
Hg = H;# in AT/m
# Ampere turn required for air gap
AT = Hg*Ig;# AT for air gap in AT
#results
print "The amphere turns for the gap in AT is",round(AT)
```

In [4]:

```
#pg 269
#calculate the total flux
# Given data
from math import pi
N = 500.;
R = 4.;# in ohm
d = 0.25;# in m
a = 700.;# in mm^2
a = a*10**-6;# in m^2
V = 6.;# in V
miu_r = 550.;
#calculations
miu_o = 4*pi*10**-7;
# Evaluation of current by ohm's law
I = V/R;# in A
l = pi*d;# in m
H = (N*I)/l;# in A/m
# Evaluation of flux density
B = miu_o*miu_r*H;# in T
# Evaluation of total flux
phi = B*a;# in Wb
phi= phi*10**3;# in mWb
#results
print "The total flux in the coil in m/Wb is",phi
```

In [5]:

```
#pg 269
#calculate the flux, density, reluctance, mmf
# Given data
from math import pi
d_r = 8;# diameter of ring in cm
d_r = d_r*10**-2;# in m
d_i = 1;# diameter of iron in cm
d_i = d_i * 10**-2;# in m
Permeability = 900;
gap = 2;# in mm
gap = gap * 10**-3;# in m
N = 400;
I = 3.5;# in A
#calculations
l_i = (pi*d_r)-gap;# length of iron in m
a = (pi/4)*(d_i**2);# in m**2
mmf = N*I;# in AT
print "The mmf in AT is",mmf
miu_o = 4*pi*10**-7;
miu_r = 900;
Si = l_i/(miu_o*miu_r*a);# in AT/Wb
miu_r = 1;
Sg = gap/(miu_o*miu_r*a);# in AT/Wb
S_T = Si+Sg;# in AT/Wb
print "The total reluctance in AT/Wb is",round(S_T,3)
phi = mmf/S_T;# in Wb
print '%s %.4e' %("The flux in Wb is",phi)
# phi = B*a;
B = phi/a;# in Wb/m**2
print "The flux density of the ring in (Wb/m^2) = ",round(B,4)
```

In [6]:

```
#pg 271
#calculate the reluctance and inductance
# Given data
from math import pi
miu_r = 1400;
l = 70;# in cm
l = l * 10**-2;# in m
a = 5;# in cm**2
a = a * 10**-4;# in m**2
N = 1000;
#calculations
miu_o = 4*pi*10**-7;
S = l/(miu_o*miu_r*a);# in AT/Wb
# Calculation of inductance of the coil
L = (N**2)/S;# in H
#results
print '%s %.3e' %("The reluctance of the magnetic circuit in AT/Wb is",S)
print "The inductance of the coil in H is",round(L,3)
print 'Note: In the book the calculated value of L is correct but at last they print its value wrong'
```

In [7]:

```
#pg 271
#calculate the current
# Given data
from math import pi
l1 = 25.;# in cm
l1 = l1 * 10**-2;# in m
miu_o = 4*pi*10**-7;
miu_r = 750;
a1 = 2.5*2.5*10**-4;# in m
S1 = l1/(miu_o*miu_r*a1);# in AT/Wb
l2 = 40;# in cm
l2 = l2 * 10**-2;# in m
S2 = l2/(miu_o*miu_r*a1);# in AT/Wb
phi2 = 2.5*10**-3;# in Wb
N = 500;
#calculations
# mmf = phi1*S1 = phi2*S2;
phi1 = (phi2*S2)/S1;# in Wb
phi = phi1+phi2;# in Wb
# Sum of mmf required for AEFB
S_AEFB = S2;# in AT/Wb
mmfforAEFB = S_AEFB*phi;# mmf for AEFB in AT
totalmmf = mmfforAEFB+(phi1*S1);# total mmf in AT
# N*I = totalmmf;
# Calculation of current
I = totalmmf/N;# in A
#results
print "The current in A is",round(I,3)
```

In [8]:

```
#pg 272
#calculate the current
# Given data
from math import pi
a = 16*10**-4;# in m**2
lg = 2*10**-3;# in m
N = 1000;
phi = 4*10**-3;# in Wb
miu_r = 2000;
miu_o = 4*pi*10**-7;
l=25.;# length of magnetic in cm
w= 20.;# in cm (width)
t= 4.;# in cm (thickness)
#calculations
li= ((w-t)*t/2+(l-t)*t/2-0.2);# in cm
li= li*10**-2;# in m
S_T= 1/(miu_o*a)*(li/miu_r+lg)
# Calculation of current with the help of flux
# phi = mmf/S_T = N*I/S_T;
I = (phi*S_T)/N;# in A
#results
print "The current in A is",round(I,3)
```

In [9]:

```
#pg 273
#calculate the total flux
# Given data
from math import pi
N = 500.;
R = 4.;# in ohm
d_mean = 0.25;# in m
a = 700;# in mm^2
a = a * 10**-6;# in m
V = 6;# in V
miu_r = 550;
miu_o = 4*pi*10**-7;
#calculations
l_i = pi*d_mean;# in m
S = l_i/(miu_o*miu_r*a);# in AT/Wb
I = V/R;# in A
# Calculation of mmf
mmf = N*I;# in AT
# total flux
phi = mmf/S;# in Wb
phi = phi * 10**6;# in muWb
#results
print "The total flux in the ring in muWb is",phi
# Note: In the book the value of flux calculated correct in muWb but at last they print only in Wb, so the answer in the book is wrong.
```

In [10]:

```
#pg 274
#calculate the current and coil inductance
# Given data
from math import pi
N = 1000.;
a = 5;# in cm**2
a = a * 10**-4;# in m**2
l_g = 2;# in mm
l_g = l_g * 10**-3;# in m
B = 0.5;# in T
#calculations
#miu_r= inf;
phi = B*a;# in Wb
miu_o = 4*pi*10**-7;
S = l_g/(miu_o*a);# in AT/Wb
# Calculation of current with the help of flux
# phi = mmf/S = N*I/S;
I = (phi*S)/N;# in A
# Evaluation of coil inductance
L = (N**2)/S;# in H
#results
print "The current required in A is",round(I,4)
print "The coil inductance in H is",round(L,4)
```

In [11]:

```
#pg 274
#calculate the amphere turns
# Given data
from math import pi
l_g = 4.;# in mm
l_g = l_g * 10**-3;# in m
Bg = 1.3;# in Wb/m**2
#calculations
miu_o = 4*pi*10**-7;
Hg = Bg/miu_o;
# Ampere turns for the gap
AT = Hg*l_g;# in AT
#results
print "The amphere turns in AT is",round(AT,2)
```

In [12]:

```
#pg 274
#calculate the mmf required
# Given data
from math import pi
phi = 0.015;# in Wb
l_g = 2.5;# in mm
l_g = l_g * 10**-3;# in m
a = 200;# in cm**2
a = a * 10**-4;# in m**2
miu_o = 4*pi*10**-7;
# Calculation of reluctance of air gap
Sg = l_g/(miu_o*a);# in AT/Wb
mmf = phi*Sg;# in AT
#results
print "The mmf required in AT is",round(mmf)
```

In [13]:

```
#pg 275
#calculate the reluctance, flux
# Given data
from math import pi
a = 12;# in cm**2
a = a * 10**-4;# in m**2
l_i = 50;# in cm
l_i = l_i * 10**-2;# in m
l_g = 0.4;# in cm
l_g = l_g * 10**-2;# in m
N = 2*400;
I = 1;# in A
miu_r = 1300;
#calculations
miu_o = 4*pi*10**-7;
Si = l_i/(miu_o*miu_r*a);# in AT/Wb
print "The reluctance of magnetic circuit in AT/Wb is",round(Si)
miu_r = 1;
Sg = l_g/(miu_o*miu_r*a);# in AT/Wb
print "The reluctance of air gap in AT/Wb is",round(Sg)
S_T = Si+Sg;# in AT/Wb
print "Total reluctance in AT/Wb is",round(S_T)
mmf = N*I;# in AT
phi_T = mmf/S_T;# in Wb
phi_T= phi_T*10**3;# in mWb
print "The total flux in mWb is",round(phi_T,5)
phi_T= phi_T*10**-3;# in Wb
# phi_T =B*a;
B = (phi_T)/a;# in Wb/m**2
print "The flux density of air gap in Wb/m^2 is",round(B,4)
```

In [14]:

```
#pg 276
#calculate the current required
# Given data
from math import pi
l = 30.;# in cm
d = 2.;# in cm
N = 500.;
phi = 0.5;# in mWb
Airgap = 1;# in mm
miu_r = 4000;
#calculations
miu_o = 4*pi*10**-7;
Ac = (pi/4)*(d**2);# in cm^2
Ac = Ac * 10**-4;# in m^2
l_i = (l*10**-2)-(Airgap*10**-3);# in m
l_g = 1;# in mm
l_g = l_g * 10**-3;# in m
Si = l_i/(miu_r*miu_o*Ac);# in AT/Wb
Sg = l_g/(miu_o*Ac);# in AT/Wb
S =Si+Sg;# in AT/Wb
# phi = mmf/S = N*I/S;
I = (phi*10**-3*S)/N;# in A
#results
print "The current required in A is",round(I,4)
```

In [15]:

```
#pg 276
#calculate the inductance
# Given data
from math import pi
l = 40;# in cm
l = l * 10**-2;# in m
a = 4;# in cm**2
a = a * 10**-4;# in m**2
miu_r = 1000;
miu_o = 4*pi*10**-7;
l_g = 1;# in mm
l_g = l_g * 10**-3;# in m
N = 1000;
#calculations
l_i = l-l_g;# in m
Si = l_i/(miu_r*miu_o*a);# in AT/Wb
Sg = l_g/(miu_o*a);# in AT/Wb
S = Si+Sg;# in AT/Wb
# The inductance of the coil
L = (N**2)/S;# in H
#results
print "The inductance of the coil in H is",round(L,4)
```