Question

According to the conductivity, pick the odd one out from the following: Glass, Copper, Iron and Gold.

Answer 1

Conductivity is defined as the ability or quality of a material to conduct or transmit any energy form. In the materials provided above, we have to find out which ones are conductors and which are insulators.

Complete step-by-step solution:
Conductivity of a material is it’s ability to conduct or transmit any energy form namely electrical energy in the form of current and thermal energy in the form of heat.
Let us now talk about electrical conductivity.
According to mathematical expression it is defined as the ratio of current density in the material to the electric field which causes the current. It can be expressed as:
$\sigma = \dfrac{{RA}}{l}$ where $A$ is the area of cross-section of the material, $R$ is the resistance of the material and $l$ is the length of the material.
The unit of conductivity is $\dfrac{S}{m}$ where $S =$ Siemens
Out of the given materials here,
The electrical conductivity at ${20^ \circ }$ $C$ of Copper is $5.96 \times {10^7}{\text{ }}\dfrac{S}{m}$
The electrical conductivity at ${20^ \circ }$ $C$ of Gold is $4.11 \times {10^7}{\text{ }}\dfrac{S}{m}$
The electrical conductivity of at ${20^ \circ }$ $C$ Iron is ${\text{1}}{{\text{0}}^7}{\text{ }}\dfrac{S}{m}$
Whereas Glass is not even an electrical conductor thus its electrical conductivity is very less and close to $0$.
So, the odd one out from the following is Glass.

Note: The insulators also has a conductivity of about ${10^{ - 16{\text{ }}}}\dfrac{S}{m}$ which is so less that it is considered to be negligible. The conductivity is of two types both electric and thermal. But, in this case all the materials given in the question conducts heat. So, no one is the odd one from the following. Therefore, only electrical conductivity is considered.