Electrical resistance of certain materials, known as superconductors, changes abruptly from a nonzero value of zero as their temperature is lowered below a critical temperature `T_(C) (0)`. An interesting property of super conductors is that their critical temperature becomes smaller than `T_(C) (0)` if they are placed in a magnetic field, i.e., the critical temperature `T_(C) (B)` is a function of the magnetic field strength B. The dependence of `T_(C) (B)` on B is shown in the figure.
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A superconductor has `T_(C) (0) = 100 K`. When a magnetic field of 7.5 Tesla is applied , its `T_(C)` decreases to 75 K. For this material one can difinitely say that when

Options

A. `B = 5 Tesla, T_(C) (B) = 80K`
B. `B= 5Tesla, 75 K lt T_(C)(B) lt 100K`
C. `B= 10 Tesla, 75ltT_(C)(B) lt100 K `
D. `B = 10 Tesla, T_(C) (B) = 70K`.

Answer

B

Explanation

(b) We know that as B increases, `T_(C)` decreases but the exact dependence is not known.
Given at `B = 0, T_(C) = 100K`
and at `B= 7.5 T, T_(C) = 75K`
`:. At B = 5T, T_(C) should be between 75 K and 100K. `