Which of the following quantities remain the same in all parts of a series circuit ____________?

The resistance of a conductor of diameter d and length l is R Ω. If the diameter of the conductor is halved and its length is doubled, the resistance will be

A. R Ω
B. 2R Ω
C. 4R Ω
D. 8R Ω

As per law of resistance, the resistance of the conductor is inversely proportional to its cross-sectional area i.e. it is inversely proportional to the square of the diameter of cross-sectional area of the conductor. As per same law of resistance, the resistance of the conductor is directly proportional to the length of the conductor.

The resistivity of the conductor depends on

A. area of the conductor.
B. length of the conductor.
C. type of material.
D. none of these.

The resistivity is a property of material, defined as the resistance between two opposite faces of a cube of a material of unit volume. That is why resistivity is only the unique property of material and it does not depend upon the dimension of any piece of material.