Semiconductors and Insulators, Properties, Applications, Practice Problems, FAQs

Anuj, while working in a physics lab, encounters a weird problem. He was working with a low voltage setup. There were two wires connected to a 10 V battery. He was barefoot at this time which he should not have been. When he touched a wire he did not feel anything weird. But while touching another wire he felt numbness in his hand. He later asked the teacher why this happened. Teacher told him that it was electricity which flew through him and he felt numbness. He was slightly electrocuted, the teacher smiled at him. He was surprised why the other wire did not feel the same. Teacher told him that the other wire was insulated. Let’s understand what conductors and insulators are in this article!

Table of content

• Conductors and Insulators in electricity
• Electrical Conductor
• Properties of Electrical Conductor
• Applications of Electrical Conductors
• Electrical Insulators
• Properties of Electrical Insulators
• Applications of Electrical Insulators
• Practice Problems
• FAQs

Conductors and Insulators in electricity 

Conductors are the materials which allow electrons to flow through them easily. 

Mostly the conductors are metals, the earth and even humans or animals are conductors. 

The human body is a good conductor of electricity. It offers a route with less resistance than a current-carrying wire. That is why in an accident people get electrocuted as current flows through the body. Conductors have free electrons which allow the easy passage of current. That is why electricity transmits freely through the conductors.

Electrical Conductor

Electrical conductors are the materials which allow electricity to flow easily through them. Aluminium, silver, copper, gold, graphite, platinum, water are the examples of electrical conductors.

Electrical conductors enable electrical charges to pass through them easily. This property of the conductors is the conductivity which actually implies to conduct electricity. Such conducting materials offer less opposition which is resistance to the movement of charges.

Properties of Electrical Conductor 

The movement of electrons and ions is easy in a conductor. 

A conductor's electrical field inside itself is zero, allowing electrons to pass easily inside it. 

There are free charges on the surface of the conductor. 

If we join two conductors, then the ends joining the conductors are at the same potential.

Usually, the metals are strong conductors of electricity. 

Applications of Electrical Conductors

In certain cases, conductors are very useful. 

Aluminium is such a metal which is used in manufacturing foils for food preservation. Aluminium is used in the manufacturing of cooking pots, vessels because of its property of being a good conductor of electricity and heat.

Iron is used to conduct heat in engine manufacturing. This is perfect to absorb the heat and then transmit heat from the chamber to the surrounding area.

Conductors are useful in car radiators as the main function of it will be to eradicate heat away from the engine. 

In checking the temperature of a body, mercury is the particular metal that is used in the thermometer. 

Electrical Insulators

The materials which resist current to pass through them are insulators. 

The material property of resistivity is the property that makes insulators different from conductors.

Some examples of insulators are fabric, glass, mica, wood and quartz. Insulators are widely used in providing protection against electricity transmission. Insulators have no or less free electrons as compared to conductors. This is why they don't conduct electricity.

Glass is one of the best insulators as it has the highest resistivity. Plastic is also a good insulator. It is used in manufacturing a variety of products including wire coating.

A common material used in the manufacture of fire-resistant clothing, tyres and slippers is rubber. This is because it is a long-lasting insulator.

Properties of Electrical Insulators

The movement of electrons and ions is not at all easy in an insulator. 

There are less or even no free charges in an insulator.

In case of an insulator the voltage drop is huge in a short distance in the direction of the current flow.

Usually, the non-metals are good insulators of electricity. 

Applications of Electrical Insulators

Insulators such as a plastic coating that covers an electrical conductor prevents us from electrical shock.

Electrical insulators are widely used in capacitors because of their dielectric property.

Electrically insulating materials are important in electrical boards and circuits which will resist the system from short circuiting. 

Practice Problems

Q 1. Why do insulators not conduct electricity?
A. Free electrons are the main constituent for the conduction of electricity, if voltage difference is applied. Insulators don’t have free electrons. Therefore, they don’t conduct electricity. Insulators are the materials which behave just the opposite way on the flow of electrons. Insulators don’t let electrons flow easily from one atom or molecule to another. Insulators are the materials whose outermost electrons are tightly bound to their atoms. So, these electrons are not free to roam around which actually helps in conducting electricity.

Q 2. Why do electrons move so easily in a conductor?
A. In metals such as silver, copper and aluminum, the electrons are not tightly bound to the atoms. So, they are called the "free electrons". This is what makes a good conductor of electricity. These are the materials which allow electricity or electrons to flow easily through them. Conductors are the materials whose outermost electrons are not that tightly bound to their atoms. If a suitable electric field is applied, these electrons easily break away. So, these electrons are free to roam around which actually helps in conducting electricity.

Q 3. Can a conductor run out of electrons?
A. When an electron is removed from a body, the remaining is a positively charged body which attracts all the electrons around it. This is just a tiny fraction of all the free electrons in the conductor. The electric field generated by the charged conductor is to overcome any electric field created by the "high voltage" applied to it. Thus, it prevents further removal of the electrons.

Q 4. Can protons move in a conductor?
A. The charge carriers here are practically always electrons which move in different directions according to the voltage applied. It is important to note that positively charged particles or protons cannot move freely as electrons flow in a conductor. If we are able to apply enough electrostatic force in terms of voltage, positive charges may find their way through the solid conductor. In that case, the solid's structure may get altered.

FAQs

Q 1. Chart out the differences between conductors and insulators of electricity.
A. The differences between electrical conductors and electrical insulators are:

Materials that permit electricity to pass through them are the conductors. Whereas, the materials which don’t permit electricity to pass through them are the insulators. 

The electrons move freely within a conductor. Whereas the electrons don’t move freely within an insulator.

Electric field exists on the surface of a conductor but it remains zero on the inside of the conductor. The electric field doesn’t exist in an insulator. 

Some examples of conductors are silver, iron, aluminium etc. Some examples of insulators are wood, plastic, paper and rubber etc.

Actually, there is no absolute or perfect conductor or insulator as such. Every object conducts electricity to a different extent because of their conductivity or resistivity. The conductors have less resistivity (more conductivity) while the insulators have more resistivity (less conductivity) as material property.

Q 2. Are all metals good conductors of electricity? 
A. Electric current, is the uniform motion of free electrons through a conductor. In case of a conductive material, the outer electrons in the atoms are loosely bound to the nuclei. They are called the free electrons. In the case of insulating materials, the outermost electrons are not free electrons. That is why usually metals are electrically conductive in nature. To be precise there is no metal which is an insulator of electricity as such. Metals are usually good conductors of electricity. But heavy metals like uranium or plutonium are not good conductors of electricity. Metals like silicon, germanium etc are semi-conductors which are actually insulators but after a threshold voltage they start conducting electricity.

Q 3. Are all nonmetals good insulators of electricity?
A. Non-metals generally cannot conduct electricity. They have no free electrons like metals.
But there is an exception. Carbon which is a non-metal, conducts electricity. The form of carbon as graphite can be classified as a semimetal. In a graphite molecule, one valence electron from each carbon atom always remains free. Thus, graphite is a good conductor of electricity. In other forms of carbon this is not possible. Let’s say, in the diamond, there is no free electron as it is in the case of graphite. So, there won’t be a flow of electrons. This is the reason why diamond is a bad conductor of electricity. There are superconducting materials like cuprates which are actually ceramics.

Q 4. Justify whether “good conductor of electricity implies good conductor of heat as well”.
A. The conduction of heat is because of the vibration of the molecules in a body. The conduction of electricity is because of the loosely bound electron in an atom or a molecule. These free electrons when under an electric field flow along the increasing potential and create electricity.

Usually, good conductors of heat are also good conductors of electricity. However, this is not always true. One of the exceptions is mica. Mica is a good conductor of heat but a bad conductor of electricity.