Question

Which of the following is an insulator?
(A) Copper
(B) Iron
(C) Sulphur
(D) Graphite

Answer 1

Hint: Think about what an insulator is. Take a look at the given options and think which one has the property of conductance of electricity. Think about wires present around you, which is the material they are made up of and the importance of coating the wires with rubber or plastic.


Complete step by step solution:
- Insulators are the materials which do not conduct electricity. These substances have a large gap between the conduction band and valence band and thus, electrons are not able to jump from conduction band to valence band.
- Conductors are the substances which have the potential to conduct electricity. These substances have a very small gap between the conduction band and valence band and thus, electrons can easily jump from conduction band to valence band and conduct electricity. Metals are very good conductors of electricity.
- In order to conduct electricity, a substance should contain ‘sea of electrons’ which are mobile.
- Let’s take a look at the options and see which among them are conductors and insulators.
- Copper is a metal and consists of free electrons. It is an excellent conductor of electricity. Electrical wires are made up of copper only.
- Iron is also a metal. It also conducts electricity.
- Sulphur is a non- metal. It doesn’t conduct electricity and therefore, it is an insulator.
- Graphite is a non-metal. It is an allotrope of carbon. Due to the movement of non-bonded electrons in between its adjacent layers, graphite does conduct electricity and therefore, graphite is a conductor.
- Therefore, sulphur is an insulator.

- The answer is option (C).



Note: Remember metals are conductors of electricity due to the presence of ‘sea of electrons’ in them. Generally, non-metals are not conductors of electricity that is, they are insulators. But graphite is an exception, it is a very good conductor of electricity. The electrical wires are made up of copper and are insulated with rubber or plastic because they are bad conductors of electricity and do not conduct electricity and thus, ensure safety from electrical shock.