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An object’s ability to transfer electric charge depends upon whether it is made of a conductive or a non-conductive material. For example, when we turn on an electric switch, the bulb glows. It is because a metallic wire is used to transfer electric current to the bulb. But, if a plastic wire or a cotton thread is used in its place, the bulb will not glow. This experiment makes it evident that some objects have the potential to transfer electric charge, while some don’t. According to their abilities, they are classified as Conductors, Semiconductors and Insulators. This article covers their definitions, examples and properties.
What are conductors?
Conductors are materials that allow electricity to flow freely and easily through them. The property of conductors which permits them to conduct electricity is called conductivity. The force required to make the flow of electrons is known as voltage.
How does a conductor work?
The conductivity of a conductor depends on the total number of charged particles present and how far they can move from one place to another. Following are some points about how conductors work:
- A conductor has free-moving electrons on its surface, which allow electricity to pass through smoothly.
- When an electric charge is transferred through a conductor, it gets distributed across its entire body due to the movement of electrons.
- Electric charges continue to spread over a conductor’s surface until the force of repulsion between the electrons in areas of surplus electrons is reduced to the minimum.
- When a conductor is brought in contact with another conductor, electric charges get transferred from the first object to the other until the charges are minimised.
- Examples of conductors: copper, silver, iron, brass, steel, gold, aluminium, etc. Even human and animal bodies are examples of conductors.
Importance of conductors in our life
- Silver is known as the best conductor of electricity as it contains a large number of movable free electrons. It is used in various specialised tools like satellites, solder and electric circuit boards.
- Copper is commonly used in household appliances and electrical equipment.
- Aluminium is often used in long-distance power lines and electrical appliances.
- Nickel is widely used in electric vehicle batteries and power generation facilities.
- Graphite is the only non-metal that can conduct electricity. It is used in making electrodes and in car batteries.
What are semiconductors?
Semiconductors are known as the ‘Brains of Modern Electronics’. Semiconductors are elements with a conductivity value between conductors and insulators.
Example: Silicon, Germanium, Arsenide, and the elements near the ‘metalloid-staircase’ on the periodic table.
Types of semiconductors
Semiconductors are divided into two types:
- Intrinsic Semiconductors
- Extrinsic Semiconductors
Intrinsic semiconductors
Intrinsic Semiconductors are created to be very pure. There is only one particular form of intrinsic semiconductors. Examples: Germanium (Ge), Silicon (Si), etc.
Extrinsic semiconductors
In Extrinsic Semiconductors, conductivity can be improved by adding impurities. The method of introducing an impurity atom into a pure semiconductor is known as doping. Extrinsic semiconductors are divided into two categories –
- N-type Semiconductor
- P-type Semiconductor
- N-type Semiconductor: Impurities like As, Sb and Bi are added into a pure semiconductor like silicon or germanium. As a result, four of the five valence electrons make a bond with the four valence electrons of Si or Ge.
- P-type Semiconductor: a pure semiconductor (Si, Ge) is doped with a trivalent impurity like Aluminium, Gallium or Arsenic. As a result, three valence electrons of the impure element make a bond with three of the semiconductor’s four valence electrons.
Comparison between Intrinsic and Extrinsic Semiconductors
Parameters | Intrinsic Semiconductors | Extrinsic Semiconductors |
Meaning/ Outline | Semiconductors are in pure form | Semiconductors are doped with impurities. |
Production of change carriers | Due to thermal agitation | Mainly due to impurities |
Electrical conductivity | Low electrical conductivity | High electrical conductivity |
Temperature | Low operating temperature | High operating temperature |
Behaviour at 0 kelvin | Fermi level stands between conduction and valence bands | In N-type semiconductors, the Fermi level lies close to the conduction band. In P-type semiconductors, the Fermi level lies near the valence band. |
Examples | Silicon, Germanium | Si and Ge are doped with Al, Ga, P etc. |
Importance of semiconductors in our life
- Semiconductors are used in temperature sensors of air conditioners.
- Semiconductors are used in designing logic gates, digital circuits, and analogue circuits like oscillators and amplifiers.
- Semiconductors are used in solar plates.
- Semiconductors are used in 3D printers and microchips.
- Semiconductor devices are used in computers, calculators, mobile phones and other electronic gadgets.
What are insulators?
Insulators are non-metal elements that have high resistance to the transmission of electricity. These materials stop electrons from moving freely from one element to another.
Examples: glass, plastics, wool, cotton, rubber, pure water etc.
How does an insulator work?
If an electric charge is applied to an insulator, it remains in the applied area and does not spread throughout the element’s body.
Methods for charging insulators:
- Induction
- Rubbing with other materials
Importance of insulators in our life
- Ceramic materials (insulators) are often used in wire holders and coating in high voltage power systems to restrict wires from conducting electricity.
- Dry cotton is a frequently used material in cloth tapes that insulates electrical wires and keeps people safe and secure.
- Fibreglass wire is an excellent insulator used in high voltage power systems like ovens or furnaces.
- Glass is typically used as an insulator in power lines.
- Rubber is an excellent insulator. Electricians use rubber gloves and shoes to protect themselves against electric shocks. Rubber is also used in switchboards and electrical sheathing.
Comparative analysis between conductors, semiconductors, and insulators
Parameters | Conductors | Semiconductors | Insulators |
Definition | A substance that allows electric charge to pass freely through it | A material whose conductivity lies between conductors and insulators | A substance that does not permit the flow of electric current |
Relationship with Temperature | With an increase in temperature, its resistance increases | With an increase in temperature, its resistance decreases | With an increase in temperature, its resistance decreases |
Conductivity | High conductivity | Intermediate conductivity | Low conductivity |
Reason of conduction | Due to the presence of free electrons in metal bonding | Due to the movement of electrons and holes | No conduction, as there are no free electrons |
Conductivity value | Very high, i.e. 10-⁷ MHO/M | Between 10-⁷ MHO/M to 10-¹³ MHO/M | Almost negligible, its 10-¹³ MHO/M |
Energy Band Gap | No energy gap exists | Its energy gap is 1 eV, which is greater than conductors but smaller than the insulators | Its energy gap is 5 eV, and it needs a huge amount of energy to push electrons |
Resistance Power | Low | Normal | Very high |
Resistivity Value | Less than 10-⁵Ω-M | Between 10-⁵Ω-M to 10-⁵Ω-M | More than 10-⁵Ω-M |
Coefficient of Resistivity | Positive Coefficient of Resistivity | Negative Coefficient of Resistivity | Negative Coefficient of Resistivity |
Number/s of valence electrons in outer shell | 1 valence electron | 4 valence electrons | 8 valence electrons |
Process of Formation | Formed by metallic bonding | Formed by covalent bonding | Formed by Ionic bonding |
Behaviour in Absolute Zero point (0 Kelvin) | Act like a super-conductor | Act as an insulator | Act as an insulator |
Conclusion
Conductors are an essential substance for electricity transmission. They have many real-life applications. On the other hand, while semiconductors have huge technology applications, insulators help reduce the risk of electrical fires and make the circuit safe to touch. Graphite is the only non-metal that can conduct electricity.Rubber is an excellent insulator.Rubber is also used in switchboards and electrical sheathing.Semiconductors are used in designing logic gates, digital circuits, and analogue circuits like oscillators and amplifiers.
