Resistivity is divided into two categories.

1. Materials with low resistance

2. Materials with high resistance

Low Resistivity Materials

These materials have become the mainstay of all electrical systems developed in recent history. Most importantly, they are characterized by their excellent capacity to conduct an electric current. This comes from the structure of their atoms that supplies a large number of free electrons that carry charge.

Resistivity: The Basics

Resistivity is a material property that refers to the resistance or opposition that a given substance offers to the flow of an electric current. The low resistivity material shall have little resistance to current flow. This can prove useful in many applications where high conductivity and low energy loss are sought.

* Consider a water pipe with low alagae that will enhance water flow. Comparably, a conductor with a low resistivity material permits the least amount of resistance loss.

Key Properties of Low Resistivity Materials

High Conductivity: Owing to free electrons in abundance within these materials, they conduct electricity very well.

Low Resistance: Their intrinsic resistance to current flow is very minimal, making them assure efficient energy transfer.

Metal Dominance: With few exceptions, most of the low resistivity materials fall under the category of metal.

Common Examples

Metals

Copper: Being one of the cornerstones of the electrical industry, copper's high conductivity, ductility, and malleability give it a prominent place for wiring, cables, and several electrical components. Its wide usage is an accreditation to its high performance.

Silver:Silver is one metal with the highest conductance. However, the high cost restricts it only to sectors of electronics, high-frequency circuits, and other applications where the highest possible conductance is a must.

Gold :Gold has low resistivity along with high corrosion resistance and stability; hence, gold finds applications in electronic connectors and integrated circuits where the components are susceptible to wear and tear, and reliable performance is required.

Aluminum: Aluminum provides an excellent weight to conductivity ratio; hence it is used in power transmission lines and electrical wirings. It also finds application in heat sinks. Its lightness offers an added advantage wherever weight reduction is necessary.

Alloys

Brass: It is an alloy of copper and zinc. It constitutes good conductivity and machinability. It finds application in electrical connectors, plumping components, and architectural decorative uses.

Bronze: Essentially an alloy of copper and tin, bronze combines conductivity with resistance to corrosion. It is used in electrical contacts and in hardware and ornaments exposed to marine environments.

Factors Affecting Resistivity

While low resistivity is an inherent property in these conductors, several factors will influence the conductivity :

Temperature: In general, when the temperature of a metal is increased, its atomic vibrations increase, leading to increased resistivity.

Impurities: The presence of impurities in the structure of material may scatter electrons and hence depressing their movement, resulting in high resistivity.

Material purity: As a rule, higher purity means lower resistivity since impurities are few or not present at all.

Crystal Structure: Arrangement of atoms in the crystal lattice affects electron mobility and hence affects its resistivity.

Applications:

The importance of the low resistivity materials is realized by their extensive applications in a number of industries:

Power Generation and Transmission: Copper and aluminum are mainly used as conductors in power grids to effectively transfer energy over a long distance.

Electronics: These form the platform from the simplest circuits to complex, highly integrated circuits that makeup electronic devices.

Telecommunications: Low resistivity metals have been the needful applied material in telecommunication systems, particularly for cables and connectors.

Transport: In electric vehicles and hybrid systems, copper and aluminum are used because of the efficacious way in which they store energy and distribute it accordingly.

Industrial Machinery: In this case, low resistivity materials are used to the maximum for motors, generators, or any other industrial equipment.

High Resistivity Materials:

High resistivity materials are materials that strongly oppose the flow of an electrical current. This property is called resistance, very important in many applications of electricity where controlled energy dissipation or isolation is required.

Resistivity Understanding

Resistivity, ρ, is an intrinsic property of a material quantifying the opposition of that material to electrical current. In high resistivity materials, the values for ρ become far larger compared to conductors. Material applications like generation of heat or electrical insulation are plentiful for such kinds of materials.

* Envision a water pipe with a significant algae content that lowers the water flow. In contrast, the least amount of resistance loss is permitted in a conductor made of a material with low resistivity.

Properties of High Resistivity Materials

Low Conductivity :Free electrons in these materials are few. Hence, it is possible to effectively transfer only a minimal charge.

High Resistivity: They have high resistance to the flow of electric current, therefore heating up when current passes through them.

Variable Constituents: High-resistivity materials can be metals, alloys, non-metals, or compounds.

Common Examples

Metals and alloys

Nichrome: Nichrome is an alloy of nickel and chromium. It is also one of the most widely used materials, with very high resistivity. It has the additional property of being resistant to oxidation. Nichrome is used in the heating elements of stoves, toasters, and hair dryers.

Constantan: This alloy of copper and nickel has stable resistivity over a broad temperature range. Constantan is used in precision resistors and also in thermocouples.

Manganin: Another copper-nickel alloy, manganin, has a very low temperature coefficient of resistance, which makes it particularly useful for standard resistors.

Non-Metals

Carbon: While carbon has a moderate value of resistivity in its pure form, nevertheless, it is extensively used in resistors and other electrical components since its properties can be controlled quite easily.

Silicon Carbide: This ceramic material has high resistivity and is applied to heating elements and electrical insulation.

Applications of High Resistivity Materials

Heating Elements: Nichrome and other high resistivity alloys form the backbone of heating devices that convert electrical energy into heat through resistive losses. Resistors: It forms an integral part of any electronic circuit and is manufactured from high resistivity materials to control current flow and voltage levels.

Thermistors: Such temperature-sensitive resistors make use of the changes of resistivity of certain materials with temperature for the purpose of measurement and control.

Electrical Insulation: High resistivity materials like rubber, plastics, and ceramics are used so that electric shock can be avoided and circuits can be protected from damage.

Semiconductors: Although not entirely high resistivity, semiconductors like silicon have controlled resistivity, which makes them useful in transistors and diodes.

Starters: It is used for starters of electric motors

Filament: It is used for filaments for incandescent lamps.

Rheostats: It is used in rheostats (ex.,laboratory rheostats)

Factors Affecting Resistivity

There are a number of factors that affect the resistivity of the high resistivity materials:

Temperature: Generally, as temperature rises, so does resistivity because of increased vibrations of atoms.

Impurities: Impurities considerably alter the resistivity and almost always increase it.

Material Composition: The kind of elements or compounds that compose a material determine its basic resistivity.

Physical Structure: The microstructure of the material—including grain size and flaws—can be involved in modifying its resistivity.