Question

On which factor the resistance of a conductor does not depend?

• A. Its length
• B. Its area of cross-section
• C. Nature of its material
• D. Its surface finish

Hint:

For bulk DC conduction, charge flows uniformly through the entire cross-section of the conductor.
Hence, surface characteristics like polish or roughness do not alter the bulk resistance.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks to identify the factor that does not affect the electrical resistance of a conducting wire.

Step 2: Key Formula or Approach:
The resistance (\(R\)) of a uniform conductor is mathematically expressed as:
\[ R = \rho \frac{l}{A} \]
where:
\(\rho\) is the resistivity (nature of the material),
\(l\) is the length of the conductor,
\(A\) is the cross-sectional area.

Step 3: Detailed Explanation:

• Length (\(l\)): The resistance is directly proportional to the length of the conductor. As length increases, electrons experience more collisions with ions, which increases resistance.

• Area of cross-section (\(A\)): The resistance is inversely proportional to the cross-sectional area. A wider wire provides a larger path for electron flow, reducing resistance.

• Nature of material (\(\rho\)): Different materials have different free electron densities, which directly determines the resistivity and thus the resistance.

• Surface finish: At macroscopic low frequencies, electrical conduction occurs through the bulk of the conductor rather than just the surface. Therefore, the micro-roughness or surface finish of the wire has no measurable impact on its bulk electrical resistance.


Step 4: Final Answer:
Thus, the resistance of a conductor does not depend on its surface finish.