What is meant by resistance of a conductor? Name and define its SI unit. List the factors on which the resistance of a conductor depends. How is the resistance of a wire affected if:

(i) its length is doubled,

(ii) its radius is doubled?

The opposition offered by a conductor to the flow of current through it is called resistance of the conductor. The SI unit of resistance is ohm ($\Omega$). The factors on which the resistance of a conductor depends are:

(i) Length of the conductor: Resistance of a conductor is directly proportional to its length.

(ii) Area of cross-section of the conductor: Resistance of a conductor is inversely proportional to its area of cross-section.

(iii) Nature of the material of the conductor: Different materials have different resistivities.

(iv) Temperature of the conductor: Resistance of a conductor increases with increase in temperature.

(i) If the length of the wire is doubled, its resistance will also be doubled.

(ii) If the radius of the wire is doubled, its area of cross-section will increase by a factor of 4. Hence, the resistance of the wire will decrease to one-fourth.