57. Hard superconductors abserve
A. breakdown by Silsbee's rule
B. incomplete Meissner effect
C. high critical field and transition temperature
D. all of these
58. The temperature at which a conductor becomes a superconductor is called
A. Curie temperature
B. transition temperature
C. Onne's temperature
D. Neel temperature
59. Superconductivity is observed for
A. dc and low frequencies
B. high frequencies
C. microwave frequencies
D. infra-red frequencies
60. In superconducting state
A. entropy decreases which thermal conductivity increases
B. entropy increases while thermal conductivity decreases
C. both entropy and thermal conductivity increase
D. both entropy and thermal conductivity decrease
61. Superconductivity result basically due to
A. zero atomic vibration of crystal structute
B. infinite atomic vibration of crystal structure
C. all electrons having possessed fermi energy
D. all electrons interacting in the, superconducting state
62. Order of resistivity of silver is
A. pico-ohm-metre
B. milli-ohm metre
C. nano-ohm metre
D. micro-ohm metre
63. The transition temperature of most of the superconducting elements lies in the range
A. zero to 20? K
B.(c) 40? K to 60? K
C.(b) 1.14? K
D. 9.22? K
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