Question

Identify the INCORRECT statement regarding a superconducting wire

• A. transport current flows through its surface
• B. transport current flows through the entire area of cross-section of the wire
• C. it exhibits zero electrical resistivity and expels applied magnetic field
• D. it is used to produce large magnetic field

Hint:

Superconductors show zero resistance and Meissner effect, and supercurrent mainly flows near the surface within penetration depth.

Answer 1

The Correct Option is B

Step 1: Understand current flow in a superconductor.
In a superconducting wire, due to the Meissner effect, magnetic field is expelled from the interior and the current tends to flow mainly near the surface within a penetration depth.
Step 2: Check each statement.
(A) Transport current flows through its surface \(\Rightarrow\) Correct, because superconducting current is concentrated near the surface.
(B) Transport current flows through entire cross-section \(\Rightarrow\) Incorrect, because supercurrent is not uniformly distributed in the whole bulk.
(C) Zero resistivity and expels magnetic field \(\Rightarrow\) Correct (defining properties).
(D) Used to produce large magnetic field \(\Rightarrow\) Correct (used in MRI, magnets, etc.).
Step 3: Final conclusion.
Thus, the incorrect statement is (B).
Final Answer:
\[ \boxed{\text{(B) transport current flows through the entire area of cross-section of the wire}} \]