Conductor and Insulator Difference: Definitions, Examples, and Applications

Before the CBSE board exam, this table of conceptual differences between conductors and insulators will be helpful for revision. Let’s go through these first, before we look into the lengthier explanations. 

Property	Conductor	Insulator
Definition	The movement of electrons in conducting materials is free. That allows for electric current to pass through the materials from one point to another.	Insulators are materials with electrons held too close to each other to stop or block any electric current to pass through.
Examples	They are good conducting metals, including copper, aluminium, silver, and iron. Non-metal examples are graphite and even the human body.	These insulating materials would be plastic, rubber, wood, ceramic or porcelain pots.
Ability to conduct electricity	Too high a capability to conduct electricity as charges move freely, without much friction and nothing to block them.	Charges cannot move freely, which makes conductivity relatively low.
Electron mobility	Electrons can easily move through the atoms or ions in a three-dimensional arrangement, known as the lattice.	Electrons in insulators are tightly bound, as there is too high of an energy gap, at least between 3 - 9 eV.
Electrical resistance	There is an easy current flow from one atom to another that does not resist electricity in a conductor.	Insulators oppose current heavily and the resistance to electricity is quite high.
Thermal conductivity	It’s very high in conductors, as free electrons carry thermal energy that leads to the transfer of heat.	There is reduced thermal conduction in insulators, as there are few or no free electrons.
Behaviour under electric field	Electric charge can quickly redistribute across the entire surface of the conductor so that they can reduce the repulsion and achieve electrostatic equilibrium.	Electric charge in an insulator remains localised at the point of charge or contact, as electrons are held together to atoms pretty tightly. Only that particular spot shows charge, but there is no mechanism for spreading it.
Band structure	There is very little gap between the valence and conduction bands. They are close in energy levels to easily jump from the valence to the conduction bands.	In insulators, there is a massive gap between the valence and conduction bands, of greater than 3 eV, because of the atomic structure and electron configuration.
Common examples	These are the regularly used electrical wiring, cables, electronic circuits, and connectors for daily use.	Insulators are used for safety with materials such as wire coating and handle grips.

Chapter 1 of Class 12 Physics NCERT has a brief conductor definition on page 3 as,
“Substances” that “allow electricity to pass through them easily are called conductors. They have electric charges (electrons) that are comparatively free to move inside the material.”

NCERT also mentions an important inherent property of a conductor: 

“When some charge is transferred to a conductor, it readily gets distributed over the entire surface of the conductor.”

We will need to explore the mechanism of conductors below to understand this better. 

How do Conductors Work? 

Conductors are better understood through the branch of solid-state physics, which deals with physical properties at the atomic level. That will include electronic structure, as well as mechanical and thermal properties. 

Delocalised Electrons 

The main property of the conduction of a substance is knowing how free electrons exist and whether they are able to roam freely or not. Metals are good conductor examples because the valence electrons in the outermost shell in metals are loosely attracted to the nuclei. That also means that they can move freely from one atom to another. This creates a sea of delocalised electrons, and this allowed movement lets electric charge to flow quite easily. 

The Energy Bands Overlap 

In conductors, there are the conduction band and valence band that are too close to each other or overlap. A conduction band is considered to be the range that contains higher energy levels in a solid and where electrons are free to move. 

Surface Distribution of Charge 

Now, there will be little energy needed for electrons to move into the conduction band from the valence band. When you apply any charge to a conductor, it’s instantly shared across the entire surface of the particle. This exchange keeps occurring until there are fewer forces to repulse among electrons. 

Later, when you move on to learn about Continuous Charge Distribution in the same chapter, you will be dealing with calculations with real-life conductors.
There are two mathematical concepts to be aware of in this context.

Surface Charge Density

This is the amount of electric charge (ΔQ) that gets distributed per unit area (ΔS) on the surface of the conductor. The Surface Charge Density is denoted by sigma, or σ. 

The equation is 

σ = ΔQ/ΔS

If the area is too small to calculate, we will use 

σ = dQ/dS

Integrating for Continuous Distribution

We will have to use an integral for a Continuous Distribution when the total surface has a changing charge density. Here we will have to calculate the total charge, as 

$Q={\int }_s\sigma ds$

We also recommend you explore and revise with our electric charges and fields class 12 formulas, all in one place for easy access!

NCERT mentions that “non-metals like glass, porcelain, plastic, nylon, wood offer high resistance to the passage of electricity through them. They are called insulators.”

One of the important properties of insulators that differentiates them from conductors is that electrical resistivity is higher in insulators. Electrons do not flow freely in them

How do Insulators Work?

Localised Electrons

The electrons in insulators are bound together or very tightly to the atoms. A little bit of chemistry’s chemical bonding concept in Class 11 to consider here: the covalent bonds are strong in organic molecules. These are so strong that the movement of electrical conductivity is at a bare minimum. 

As charge gets transferred to an electron at a location or point, the excess charge remains still at that point. The particles cannot allow for free electron flow. 

Large Energy Gap

Unlike the conductors, there’s a large energy gap in insulators. The conduction of higher energy remains almost empty. Now that means, it will require a large energy input for electrons to flow from the valence band to the conduction band. 

Do Not Transfer Charge

Because of their high resistance, insulators cannot transfer or conduct any electrical charge. That, in fact, helps in creating barriers between conductors. Commonly, we see them in cables. 

Let’s explore a little more about conductivity. Below, you will see it’s not just the atomic natures of substances that differentiate between conductors and insulators.

How Physical Dimensions of Materials Show Conductivity

The material’s shape and size cannot be overlooked when it comes to conductivity. It boils down to the concept of resistance for a shorter piece of material against a longer piece, even when they have the same thickness. In this scenario, a shorter piece will show lesser resistance than the longer one. 

How Temperature Affects Conductivity

Atoms in conductors start to vibrate more as the temperature increases. Electrons start colliding more. In substances, such as metals, conductivity reduces when they are heated. But for an insulator, that would be different. How? Insulators, such as glass, do not conduct electricity at normal and colder temperatures. But when heated, they can conduct electricity. 

Adding Impurities Can Make Insulators Conduct Electricity

Pure water when it is in distilled form is an insulator. It can become a conductor when impurities are added, a process well known as doping. One simple example is saltwater. It conducts well because of free-floating ions. 

By now, you can already guess which could be a good conductor or insulator in the real world. But for exam's sake, we are going to list some of the strong conductor and insulator examples so you do not forget. 

Strong Conductors Examples for Class 12 Physics 

Silver, gold, copper, aluminium, iron, steel, graphite, seawater, and the human body are some of the most well-known conductor examples. 

Strong Insulators Examples for Class 12 Physics 

Some of the strong insulator types would be rubber, glass, plastic, pure water, oil, dry wood, and ceramics.

So, let’s look into the real-life scenarios where these examples can be applied. 

Applications of Insulators vs Conductors

Conductors allow for current to flow in electrical circuits. Beyond that, they also allow for heat to pass through, ie, thermal energy transfer. For instance, you can see how aluminium's thermal energy allows it to store heat quickly. The frying pan that we use daily is one real-life application of a conductor at work. 

Insulators, in general, are used as safety barriers. They are used for preventing electric shocks and short circuits in homes. Insulators like plastic or rubber are great for coating electrical wires. 

The questions for exams that you should prepare will be on broader and related concepts of the whole chapter on electric charges and fields Class 12. Prepare for interrelated concepts as below. 

• Understanding how to deal with the static distribution of charges on conducting surfaces and the concept of induced charges.
• Knowing how the dynamic redistribution of charge happens when conductors interact and the practical applications of these principles.

Along with these, go practice the Class 12 Physics Ch 1 NCERT Solutions. 

 

 

You can check the complete study material for Class 12 CBSE exams based on NCERT Textbooks. Check below;

Complete CBSE Class 12 Study Material
NCERT Class 12 Maths Solutions	NCERT Physics Class 12 Solutions	Class 12 Chemistry NCERT Solutions
Class 12 Maths NCERT Notes	Physics Class 12 NCERT Notes	Class 12 Chemistry NCERT Notes
CBSE Sample papers for class 12 Maths	CBSE Class 12 Physics Sample Papers	CBSE Class 12 Sample Paper for Chemistry
CBSE Class 12 Maths Previous Year Question Papers	CBSE Class 12 Physics Previous Year Question Papers	CBSE Chemistry Class 12 Question Papers