What are Conductors?

Definition: Substances through which electricity is easily transmitted are called conductors. In general, all metals are conductors of electricity. For example - gold, silver, copper, aluminum, mercury, etc.

In the case of any metallic conductor, the electrons in the outermost shell of the atom are relatively loosely bound to the atom. As a result, at normal temperatures, most of which are detached from atoms and move at irregular motions in the matter. These electrons are known as free electrons.

When an electric field is applied to the conductor, under the influence of the applied electric field these free electrons acquire a velocity as opposed to the electric field, which is called the drift velocity. As a result, electricity flows through the conductors.

Conductor Vs Insulator Vs Semiconductor

As the substances like copper and gold are good conductors of electricity, they are also good conductors of heat. But when the temperature increases, the resistance of this conductor increases. As a result, the conductivity of the conductive material decreases.

When the surface of a metal conductor is heated to a suitable temperature thermal ions are emitted, this phenomenon is called thermionic emission.

Also when the light of a suitable wavelength falls on a metal conductor, electrons are emitted from the metal surface, this phenomenon is called photoelectric effects.

Applications of conductors

1. Conductors are used for making cooking equipment (like pans, and fryers). The heating parts of cookware are made of conductors like steel, aluminum, copper, iron, etc.

2. Copper is a pure metal that has high electrical conductivity, so it is used in wired cables and coaxial cables for transmitting electricity.

3. Mercury is a liquid conductor that is used in thermometers to check body temperature.

What are Insulators?

Definition: Substances through which electricity cannot be easily transmitted are called non-conductive substances or insulators. For Example - plastic, wood, glass, quartz, diamonds, etc.

Insulators do not contain any free electrons, all the electrons are firmly attached to the nucleus of the corresponding atom. As a result, when a normal electric field is applied, no electricity flows through these substances.

As the substances like plastic and wood are bad conductors of electricity (but good insulators), they are also bad conductors of heat. But when the temperature increases, the resistance of this conductor increases.

As a result, the conductivity of the conductive material decreases. However, with increasing or decreasing temperature there is no change in the resistance of the insulator.

Applications of insulators

1. Insulators are also used for making cooking equipment. The handlebar of cookware (like pans, and fryers) is also made of insulators.

2. Insulators like PVC are also used for coating electrical wires and cables.

3. Fur, wool, and cotton wool are insulators used for making clothes that keep us warm during winter.

What are Semiconductors?

We know that substances that conduct electricity are called conductors (such as copper and gold), and those that do not conduct electricity are called insulators (such as wood and glass). But there are some substances whose electrical conductivity falls between the conductors and insulators they are called semiconductors.

These types of substances are found in Group-14 of the Periodic Table. Elements like Germanium(Ge), Silicon(Si), and Gallium Arsenide(GaAs) are examples of semiconductors. Silicon is mostly used in the electronic circuit for fabrication and gallium arsenide is used in LEDs, solar cells, laser diodes, etc.

At absolute zero temperature (0K), there are no free electrons in the pure semiconductors. As a result, they act as a bad conductor of electricity at this temperature. In this state, each atom is strongly bound in its covalent bond with the surrounding atom. So there are no free electrons in the semiconductor at low temperature.

But when the temperature rises and the semiconductor is heated to room temperature, the thermal excitation breaks the covalent bonds of several atoms. As a result, a number of electrons are released from the bond and move freely in the crystal. In this condition the electrical conductivity of the semiconductor increases.

The higher the temperature of the semiconductor, the more covalent bonds are broken and free electrons are formed. As a result, the electrical conductivity of the semiconductor increases with increasing temperature. That is, the resistance of the semiconductor decreases with increasing temperature.

The electrical conductivity of the semiconductor is significantly increased when a very small amount of suitable impurities is mixed with the semiconductor in a special way. The process of mixing these impurities with semiconductors is called doping.

Applications of semiconductors

We cannot think of the world without electronic devices (such as mobile phones, laptops, refrigerators, etc.). In all these devices we use semiconductor components (such as diodes, transistors, MOSFETs, ICs, etc.) which are made of semiconductor materials.

Microcontrollers/Microprocessors are such systems that revolutionized the world. These systems used nano transistors ( semiconductor components ) that act as smart switches in the systems.

There are many diodes made of semiconductor material that consume light energy to produce an electric current. For example Photodiodes (solar cells ).

There are many diodes made of semiconductor material that consumes electric current and emit light. For example LEDs.

So, semiconductors play a very important role in our daily life.

Types of semiconductors

There are two types of semiconductors - Pure or Intrinsic Semiconductor and Impure or Extrinsic Semiconductor. Know more...

But before understanding these types of semiconductors, you need to look at some key points, such as the Band Theory of Semiconductors, and Charge Carriers in Semiconductors (such as holes, and electrons).