The superconducting transition temperature of lead is 7.26K.

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The superconducting transition temperature of lead is 7.26K. If the initial field at 0 K is 64 × 10³ amp/m, then the critical field at 5 K is:

1. 0.3364 × 10³ amp/m
2. 0.364 × 10³ amp/m
3. 33.640 × 10³ amp/m
4. 336.400 × 10³ amp/m

Correct Option: C

Field intensity at temperature T is given by relation

H (T) = H₀		1 –	T²
			T_C²

where, H (T) = Field intensity at temperature T
T_C = Critical temperature/transition temperature
H₀ = Field intensity at zero degree kelvin
Given TC = 7·26° K
T=5° K
H₀ = 64 × 10³ amp/m
H (T) =?

Now, H (T) = 64 × 10³		1 –		5		²
				7.26

= 33.64 × 10³ amp/m