Conductors, semiconductors and insulators

Materials are classified as conductors, insulators, or semiconductors according to their electric conductivity. The classifications can be understood in atomic terms. Electrons in an atom can have only certain well-defined energies, and, depending on their energies, the electrons are said to occupy particular energy levels. In a typical atom with many electrons, the lower energy levels are filled, each with the number of electrons allowed by a quantum mechanical rule known as the Pauli exclusion principle. Depending on the element, the highest energy level to have electrons may or may not be completely full. If two atoms of some element are brought close enough together so that they interact, the two-atom system has two closely spaced levels for each level of the single atom. If 10 atoms interact, the 10-atom system will have a cluster of 10 levels corresponding to each single level of an individual atom. In a solid, the number of atoms and hence the number of levels is extremely large; most of the higher energy levels overlap in a continuous fashion except for certain energies in which there are no levels at all. Energy regions with levels are called energy bands, and regions that have no levels are referred to as band gaps.

Conductors

Conductors are the materials or substances which allow electricity to flow through them. They are able to conduct electricity because they allow electrons to flow inside them very easily. Conductors have this property of allowing the transition of heat or Light from one source to another. Metals, humans, earth, and animal bodies are all conductors. This is the reason we get electric shocks! The main reason is that being a good conductor, our human body allows a resistance-free path for the current to flow from wire to our body. Conductors have free electrons on its surface which allows current to pass through. This is the reason why conductors are able to conduct electricity.

Examples of Conductors

Silver is the best conductor of electricity. However, it is costly and so, we don’t use silver in industries and transmission of electricity.
Copper, Brass, Steel, Gold, and Aluminium are good conductors of electricity. We use them mostly in electric circuits and systems in form of wires.
Mercury is an excellent liquid conductor that finds use in many instruments.
Gases are not good conductors of electricity as the particles of matter are quite far away and thus, they are unable to conduct electrons.

Semiconductors

Semiconductor, any of a class of crystalline solids intermediate in electrical conductivity between a conductor and an insulator. Semiconductors are employed in the manufacture of various kinds of electronic devices, including diodes, transistors, and integrated circuits. Such devices have found wide application because of their compactness, reliability, power efficiency, and low cost. As discrete components, they have found use in power devices, optical sensors, and light emitters, including solid-state lasers. They have a wide range of current- and voltage-handling capabilities and, more important, lend themselves to integration into complex but readily manufacturable microelectronic circuits. They are, and will be in the foreseeable future, the key Elements for the majority of electronic systems, serving communications, signal processing, computing, and control applications in both the consumer and industrial markets.

Solid-state materials are commonly grouped into three classes: insulators, semiconductors, and conductors. (At low temperatures some conductors, semiconductors, and insulators may become superconductors.) The figure shows the conductivities σ (and the corresponding resistivities ρ = 1/σ) that are associated with some important materials in each of the three classes. Insulators, such as fused quartz and glass, have very low conductivities, on the order of 10−18 to 10−10 siemens per centimetre; and conductors, such as aluminum, have high conductivities, typically from 104 to 106 siemens per centimetre. The conductivities of semiconductors are between these extremes and are generally sensitive to temperature, illumination, magnetic fields, and minute amounts of impurity atoms. For example, the addition of about 10 atoms of boron (known as a dopant) per million atoms of silicon can increase its electrical conductivity a thousand fold.

The study of semiconductor materials began in the early 19th century. The elemental semiconductors are those composed of single species of atoms, such as silicon (Si), germanium (Ge), and tin (Sn) in column IV and selenium (Se) and tellurium (Te) in column VI of the periodic table. There are, however, numerous compound semiconductors, which are composed of two or more elements. Gallium arsenide (GaAs), for example, is a binary III-V compound, which is a combination of gallium (Ga) from column III and arsenic (As) from column V. Ternary compounds can be formed by elements from three different columns—for instance, mercury indium telluride (HgIn2Te4), a II-III-VI compound. They also can be formed by elements from two columns, such as aluminum gallium arsenide (AlxGa1 − xAs), which is a ternary III-V compound, where both Al and Ga are from column III and the subscript x is related to the composition of the two elements from 100 percent Al (x = 1) to 100 percent Ga (x = 0). Pure silicon is the most important material for integrated circuit applications, and III-V binary and ternary compounds are most significant for light emission.

Insulators

Insulators are the materials or substances which resist or don’t allow the current to flow through them. They are mostly solid in nature and are finding use in a variety of systems. They do not allow the flow of heat as well. The property which makes insulators different from conductors is its resistivity. Wood, cloth, glass, mica, and quartz are some good examples of insulators. Insulators are also protectors as they give protection against heat, Sound and of course passage of electricity. Insulators don’t have any free electrons and it is the main reason why they don’t conduct electricity.

Conductors

A conductor is a material that allows electricity or heat to flow through it easily. Metals, alloys, and electrolytes are all good conductors.

Metals

Metals are the most common type of conductor. They are made up of atoms that have a lot of free electrons. These electrons are not attached to any particular atom, and they can move freely around the Metal. This makes metals good conductors of electricity.

Alloys

Alloys are mixtures of two or more metals. They are often used to make conductors that are stronger or more durable than pure metals. For example, the Alloy steel is used to make car parts because it is strong and can withstand a lot of wear and tear.

Electrolytes

Electrolytes are solutions that contain ions. Ions are atoms or Molecules that have a positive or negative charge. When an electric current is passed through an electrolyte, the ions move towards the oppositely charged electrode. This movement of ions is what allows electricity to flow through an electrolyte.

Semiconductors

Semiconductors are materials that have electrical conductivity between that of a conductor and an insulator. They are used in a wide variety of electronic devices, including computers, cell phones, and solar panels.

Intrinsic semiconductors

Intrinsic semiconductors are made of pure semiconductor materials, such as silicon or germanium. These materials have a small number of free electrons. When an electric field is applied to an intrinsic semiconductor, the free electrons move towards the positive electrode and the holes move towards the negative electrode. This movement of electrons and holes is what allows electricity to flow through an intrinsic semiconductor.

Extrinsic semiconductors

Extrinsic semiconductors are made by adding a small amount of a dopant to a pure semiconductor material. The dopant can be an impurity atom, such as phosphorus or boron. When a dopant is added to a semiconductor, it creates either an n-type semiconductor or a p-type semiconductor.

N-type semiconductors

N-type semiconductors are made by adding a dopant that has five valence electrons, such as phosphorus. When a phosphorus atom is added to a silicon crystal, it forms a covalent bond with four of the silicon atoms. The fifth valence electron of the phosphorus atom is not used in a covalent bond, and it is free to move around the crystal. This free electron makes the n-type semiconductor a conductor of electricity.

P-type semiconductors

P-type semiconductors are made by adding a dopant that has three valence electrons, such as boron. When a boron atom is added to a silicon crystal, it forms covalent Bonds with three of the silicon atoms. The fourth valence electron of the silicon atom is not used in a covalent bond, and it is free to move around the crystal. This free hole makes the p-type semiconductor a conductor of electricity.

Insulators

Insulators are materials that do not allow electricity or heat to flow through them easily. Dielectrics and non-metals are both good insulators.

Dielectrics

Dielectrics are materials that are good insulators of electricity. They are often used to make capacitors, which are devices that store electrical charge. Dielectrics are made of materials that have a high dielectric constant. The dielectric constant is a measure of how easily an electric field can be established in a material.

Non-metals

Non-metals are elements that are not metals. They are usually poor conductors of electricity and heat. Some common non-metals include carbon, nitrogen, Oxygen, and sulfur.

What is a conductor?

A conductor is a material that allows electricity to flow through it easily. Metals are good conductors of electricity.

What is a semiconductor?

A semiconductor is a material that has electrical conductivity between that of a conductor and an insulator. Semiconductors are used in many electronic devices, such as computers and cell phones.

What is an insulator?

An insulator is a material that does not allow electricity to flow through it easily. Rubber and plastic are good insulators.

What are the properties of conductors?

Conductors have the following properties:

They allow electricity to flow through them easily.
They are good heat conductors.
They are shiny.
They are malleable (can be hammered into thin sheets) and ductile (can be drawn into wires).

What are the properties of semiconductors?

Semiconductors have the following properties:

They have electrical conductivity between that of a conductor and an insulator.
Their conductivity can be changed by adding impurities or by applying a voltage.
They are used in many electronic devices, such as computers and cell phones.

What are the properties of insulators?

Insulators have the following properties:

They do not allow electricity to flow through them easily.
They are poor heat conductors.
They are dull.
They are brittle (break easily).

What are the uses of conductors?

Conductors are used in many applications, including:

Electrical wiring
Power transmission
Electronics
Heating and cooling

What are the uses of semiconductors?

Semiconductors are used in many applications, including:

Computers
Cell phones
Solar cells
Transistors

What are the uses of insulators?

Insulators are used in many applications, including:

Electrical insulation
Heat insulation
Packaging
Building materials

Sure, here are some MCQs without mentioning the topic Conductors, semiconductors and insulators:

Which of the following materials is a good conductor of electricity?
(A) Wood
(B) Plastic
(C) Copper
(D) Rubber
Which of the following materials is a good insulator of electricity?
(A) Wood
(B) Plastic
(C) Copper
(D) Rubber
Which of the following materials is a semiconductor?
(A) Silicon
(B) Germanium
(C) Gallium arsenide
(D) All of the above
What is the difference between a conductor and an insulator?
(A) A conductor allows electricity to flow through it, while an insulator does not.
(B) A conductor is a material that is good at conducting heat, while an insulator is a material that is good at insulating heat.
(C) A conductor is a material that is good at conducting electricity, while an insulator is a material that is good at insulating electricity.
(D) A conductor is a material that is good at conducting sound, while an insulator is a material that is good at insulating sound.
What is the difference between a semiconductor and a conductor?
(A) A semiconductor is a material that is good at conducting electricity at high temperatures, while a conductor is a material that is good at conducting electricity at low temperatures.
(B) A semiconductor is a material that is good at conducting electricity at low temperatures, while a conductor is a material that is good at conducting electricity at high temperatures.
(C) A semiconductor is a material that is good at conducting electricity in the middle of the range of temperatures, while a conductor is a material that is good at conducting electricity at either end of the range of temperatures.
(D) A semiconductor is a material that is good at conducting electricity, while a conductor is a material that is not good at conducting electricity.
What are some common uses of conductors?
(A) Electrical wiring
(B) Batteries
(C) Circuit breakers
(D) All of the above
What are some common uses of insulators?
(A) Electrical insulation
(B) Heat insulation
(C) Sound insulation
(D) All of the above
What are some common uses of semiconductors?
(A) Transistors
(B) Diodes
(C) Solar cells
(D) All of the above
What is the resistance of a conductor?
(A) The measure of how difficult it is for electricity to flow through a material.
(B) The measure of how easy it is for electricity to flow through a material.
(C) The measure of how much electricity can flow through a material.
(D) The measure of how little electricity can flow through a material.
What is the resistivity of a material?
(A) The measure of how difficult it is for electricity to flow through a material.
(B) The measure of how easy it is for electricity to flow through a material.
(C) The measure of how much electricity can flow through a material.
(D) The measure of how little electricity can flow through a material.

I hope these MCQs are helpful!