Question

Which are good insulators?
(This question has multiple correct options.)
A) Wood
B) Copper
C) Human body
D) Glass

Answer 1

A material based on how good it conducts electricity, can either be a conductor or an insulator. Conductors conduct electricity and insulators do not. Insulators and conductors are chosen for industrial use based on the type of material. It is the property of the material which makes is a conducting or insulating substance.

Complete step by step answer:
Based on the conductivity property of a material it can be a conductor or an insulator. An insulator is a material in which the electron does not flow freely. Which means conduction of current does not take place through an insulator.
Insulators can be distinguished from semiconductors and conductors by their high resistivity.
Non-metals generally have higher resistivity than conductors.

So the correct answers are (A) and (D), because wood and glass are non metals.

Additional information:
Resistivity is the property of a material.
It is denoted by the sign $\rho$.
The resistivity of a material is related to the resistance of the conductor by the following relation,
$R = \rho \dfrac{l}{A}$
Where, $R$ is the resistance of the conductor
$\rho$ is the resistivity of the material of the conductor
$l$ is the length of the conductor
$A$ is the cross-sectional area of the conductor

Normally the value of resistivity is higher for insulators than semiconductors and conductors.

Note: Metals have lower resistivity values so they act as good conductors of electricity.
The order of resistivity increases in the following manner
**Conductors < Semiconductors < Insulators **
Temperature also affects conducting property of a substance. It is measured by a physical quantity, temperature coefficient of resistance. It has negative value for insulators and positive value for conductors, which means resistance of insulators decreases on rising temperature and resistance of conductors increases upon rise in temperature.