Physics Group - II (3110018)

BE | Semester-1   Winter-2019 | 02-01-2020

Q5) (b)

Calculate the critical current for a superconducting wire of lead having a diameter of 2 mm at 2 K. Critical temperature for lead is 4 K and Hc(0) = 6.5 X 104 A/m.

Here, Tc = Critical Temperature  = 4 K

Here, T = Temperature  = 2 K

Here, r = Redius  = D2 = 22 mm = 1 mm = 1 × 10-3 m

Here, H0 = Critical Field at 0  = 6.5 × 104 T

Now,  Hc = H0   1 - T  Tc 2 

                =  6.5 × 104 ×    1 - 2  4 2 

                =  6.5 × 104 ×    1 - 0.25 

                =  4.8 × 104  T

Now, Critical current 

 Ic = 2 π r Hc

  Ic = 2 × 3.14 × 1 × 10-3 × 4.8 × 104

  Ic = 301.44 A