Question

The length of a conductor is halved, its conductivity will be
(A) Halved
(B) Doubled
(C) Quadrupled
(D) Unchanged

Answer 1

Hint: Conductivity of a material is its ability to conduct electric current. Electrical conductivity is an intrinsic property and therefore it depends on the nature of the material and is independent of its dimensions like length, area and volume.

Complete step by step answer:
 Conductivity, also called specific conductance, is reciprocal of resistivity. We must be aware that the terms ‘Conductance’ and ‘Specific Conductance’ or ‘Conductivity’ are different from each other. Conductance of a material depends on its dimensions therefore we say conductance varies with the length and cross-sectional area of the conductor. But if we talk about conductivity, it remains the same for a given material. It is independent of the shape, size or mass of the conductor.
The relation between conductance and conductivity is given by the formula,
\[G = \sigma \dfrac{A}{l}\]
\[G\] is the conductance
\[\sigma \] is the specific conductance or conductivity
\[A\] is the cross-sectional area of the conductor
\[l\] is the length of the conductor
Thus, whatever be the length of the conductor, the conductivity for the given material will remain the same. So, if the length of a conductor is halved, its conductivity will be unchanged.

Hence the correct option is D.

Note: Metals are most conductive while Insulators are the least conductive. The metal which has the highest electrical conductivity is silver. It is taken as the standard against which the electrical conductivity of other metals is measured. After silver, copper and gold are also among good conductors. Though mercury is also a metal but pure mercury has least conductivity. Copper is used in wires because of its good conductivity, reliability and strength.