#importing modules
import math
from __future__ import division
#Variable declaration
H0=0.0106; #critical field at 0K(Tesla)
T=3; #temperature(K)
Tc=4.7; #temperature(K)
#Calculation
Hc=H0*(1-(T/Tc)**2); #critical field at 3K(Tesla)
#Result
print "critical field at 3K is",round(Hc,6),"Tesla"
print "answer given in the book is wrong"
#importing modules
import math
from __future__ import division
#Variable declaration
H0=5*10**5/(4*math.pi); #critical field at 0K(Tesla)
Tc=2.69; #temperature(K)
Hc=3*10**5/(4*math.pi); #critical field(Tesla)
#Calculation
T=Tc*math.sqrt(1-(Hc/H0)); #temperature(K)
#Result
print "temperature of superconductor is",round(T,3),"K"
#importing modules
import math
from __future__ import division
#Variable declaration
H0=6.5*10**4; #critical field at 0K(Tesla)
Tc=7.28; #temperature(K)
T=4.2; #temperature(K)
r=1.5*10**-3; #radius(m)
#Calculation
Hc=H0*(1-(T/Tc)**2); #critical field(Tesla)
Ic=2*math.pi*r*Hc; #critical current of the wire(A)
#Result
print "critical field is",round(Hc/10**4,4),"*10**4 A/m"
print "critical current of the wire is",int(Ic),"A"
#importing modules
import math
from __future__ import division
#Variable declaration
m1=199.5; #isotopic mass
m2=205.4; #change in mass
Tc1=4.185; #temperature of mercury(K)
#Calculation
Tc2=Tc1*math.sqrt(m1/m2); #critical temperature(K)
#Result
print "critical temperature is",round(Tc2,3),"K"
#importing modules
import math
from __future__ import division
#Variable declaration
T1=3; #temperature(K)
T2=8; #temperature(K)
lamda1=39.6; #penetration depth(nm)
lamda2=173; #penetration depth(nm)
#Calculation
x=(lamda1/lamda2)**2;
Tc4=(T2**4-(x*T1**4))/(1-x);
Tc=Tc4**(1/4); #superconducting transition temperature(K)
#Result
print "superconducting transition temperature is",round(Tc,3),"K"