Question

The specific resistance of a wire
A. Varies with its length
B. Varies with its cross-section
C. Varies with its mass
D. Does not depend upon its length, cross section and mass.

Answer 1

Hint- As we know the property of a material which opposes the flow of electrons is known as resistance. Specific resistance of a conductor is the resistance of a conductor of unit length and unit area of cross section. Specific resistance is a property of a material while resistance is not.

Step-By-Step answer:
Resistance increases with length and decreases with area of cross section, but specific resistance does not. It is a characteristic property of a material and in turn depends on the collisions or scattering of electrons. The specific resistance of different materials varies in an enormous amount. The specific resistance depends upon the number of electrons, the temperature of the room and other factors of material properties such as impurities in the material.

Thus it is independent upon the dimensions of wire and mass.
Hence, correct option “D”.

Additional information-
Conductivity is a measurement of the ease with which an electrical charge or heat will flow through a device. The conductor is a substance that provides relatively little resistance to the flow of electrical current or thermal energy. Depending upon conductivity materials are classified as metals, semiconductors and nonmetals. Metals are the most conductive and the least conductive insulators (ceramics, wood, plastics).

Note- Also, collisions increase with temperature, so resistivity depends upon temperature. Hence specific resistance does depend upon the temperature. Also keep in mind that the resistance and specific resistance are two different terms and resistance of a material depends upon length and cross- section of the material.