Question

Specific resistance of a conductor increases with:
(A). Increase in temperature
(B). Increase in cross section area
(C). Increase in cross section and decrease in length
(D). Decrease in cross section area

Answer 1

Hint: The specific resistance of a conductor is defined as the resistance of a part of the conductor of unit length and unit cross sectional area at a specific temperature. The specific resistance of a material of conductor remains constant whatever be the shape and size of the conductor.

Complete step by step answer:

The specific resistance of a conductor material is a fixed property of the material. The specific resistance of a conductor material is the resistance at a specific temperature of a body of unit length and unit cross sectional area made of this material. It is a constant for the material regardless of the shape and size of the body.
As defined above, the specific resistance is defined for a unit length and cross sectional area of the material. Hence, it does not depend on the total length or cross sectional area of a conducting body made of that material.
However, it is dependent on the temperature of the body. When temperature increases, the atoms in the structure of the conductor start vibrating more vigorously and hence offer an opposition to the flow of current. This increases the overall resistance of the material and hence the specific resistance also increases.
Therefore, the correct option is A) increases with temperature.

Note: Students must remember that for conductors specific resistance increases with temperature, however for semiconductors it decreases. This is because semiconductors do not have a lot of free charge carriers (electrons) at room temperature. However, as temperature increases more and more electrons gain energy and can break their bonds to act as free charge carriers and help in conducting electricity (decrease resistance).
Therefore, semiconductors are said to have a negative temperature coefficient of resistivity (specific resistance increases with decrease in temperature) while conductors are said to have a positive temperature coefficient of resistivity (specific resistance increases with increase in temperature).