Question

Which of the following is/are insulators?
$
  (a){\text{ Wood}} \\
  {\text{(b) Aluminium}} \\
  {\text{(c) Both (a) and (b)}} \\
  {\text{(d) None of (a) and (b)}} \\
 $

Answer 1

Hint – In this question use the concept that a material that does not have free electrons can’t conduct electricity that thus it is insulator. Metals are generally a very good conductor of electricity. Use them to find the right option that suits best as an insulator.

Complete answer:
Materials that are poor conductors of electricity are called insulators.
Some examples are wood, glass, plastics, non-metal elements that are polymers of hydrocarbons.
The reason that they do not conduct electricity is that charges cannot move through them the particles and their electrons are locked into a solid structure.
So among the following options aluminum is metal and wood is non-metal.
So wood is an insulator.
So this is the required answer.

Hence option (A) is the correct answer.

Note – Wood is a natural insulator due to air pockets within its cellular structure, these air pockets prevent any kind of motion of electrons and thus it can’t conduct. Moreover it doesn't have free mobile electrons either. In metals like aluminum the valence electrons are already detached due to metallic bonds between atoms and thus are free to move, this adds up to their conductivity.