Electrical resistance and conductance

Electrical resistance and conductance are two fundamental concepts in electrical engineering and physics that describe how materials respond to the flow of electric current. ### Electrical Resistance **Definition**: Electrical resistance is a measure of the opposition that a material offers to the flow of electric current. It is denoted by the symbol \( R \). **Unit**: The unit of resistance is the ohm (Ω).

Impedance measurements refer to the assessment of an electrical component's or circuit's impedance, which is a measure of how much it resists the flow of alternating current (AC) at a specific frequency. Impedance is a complex quantity, denoted as \( Z \), that combines both resistance (real part) and reactance (imaginary part).

Resistive components are electronic elements that provide resistance to the flow of electric current. Their primary characteristic is that they convert electrical energy into heat via Joule heating when current passes through them. The most common resistive components include: 1. **Resistors**: These are specifically designed to offer a certain amount of resistance in a circuit.

Semiconductors are materials whose electrical conductivity falls between that of conductors (like metals) and insulators (like glass). This unique property allows them to control electrical current, making them essential for a wide range of electronic devices. Semiconductors are usually made from elements such as silicon, germanium, and gallium arsenide.

The unit of electrical conductance is the siemens (S). It is defined as the reciprocal of electrical resistance, which is measured in ohms (Ω). Therefore, 1 siemens is equivalent to 1/ohm or \( S = \frac{1}{\Omega} \). Additionally, in other contexts, conductance can also be expressed in terms of mhos (℧), which is simply ohms spelled backward, although this terminology is less commonly used today.

The unit of electrical resistance is the ohm, symbolized by the Greek letter omega (Ω). Electrical resistance is a measure of the opposition that a circuit or material presents to the flow of electric current. One ohm is defined as the resistance between two points in a conductor when a constant potential difference of one volt applied across those points produces a current of one ampere.

Charge transport mechanisms refer to the processes by which charge carriers (such as electrons and holes) move through a material. These mechanisms are critical for understanding electrical conductivity in various materials, including semiconductors, insulators, and superconductors. Here are some key charge transport mechanisms: 1. **Drift**: - This is the movement of charge carriers due to an applied electric field.

Contact resistance refers to the resistance to current flow that occurs at the interface between two conductive materials, such as metal contacts or between a conductor and a semiconductor. This resistance is typically very small compared to the bulk resistance of the materials involved, but it can significantly affect the overall performance of electronic devices, electrical connections, and circuits.

The current-voltage (I-V) characteristic is a fundamental relationship in electronic devices that describes how the current flowing through a device varies with the applied voltage across it. This characteristic is crucial for understanding the behavior of various electronic components such as diodes, transistors, resistors, and more.

Electrical resistivity is a measure of how strongly a material opposes the flow of electric current. Different elements have varying resistivities based on their atomic structure and bonding. Here is a list of selected elements and their typical electrical resistivities at room temperature (approximately 20°C or 68°F): 1. **Silver (Ag)** - 1.59 x 10^-8 Ω·m 2. **Copper (Cu)** - 1.

An insulator, in the context of electricity, is a material that does not allow the easy flow of electric current. This is due to the high resistance of insulators in comparison to conductors (which allow electrical current to flow freely) and semiconductors (which have properties between conductors and insulators). Key characteristics of insulators include: 1. **High Resistance**: Insulators have very high electrical resistivity, meaning they resist the flow of electric charges.

Internal resistance refers to the opposition to the flow of electric current within a power source, such as a battery or a fuel cell. It occurs due to various factors, including the chemical reactions occurring inside the battery, the physical properties of the materials used in the battery, and any ionic conductivity limitations within the electrolyte. When a current flows from a power source, internal resistance causes some of the voltage to be lost as heat instead of contributing to the output voltage available to an external load.

The Kondo effect is a phenomenon observed in condensed matter physics, specifically in systems that include magnetic impurities within a metal or semiconductor. Named after Japanese physicist Jun Kondo, who first described the effect in 1964, it relates to the behavior of conduction electrons in the presence of localized magnetic moments, such as those caused by impurity atoms.

Ohm's Law is a fundamental principle in electrical engineering and physics that defines the relationship between voltage, current, and resistance in an electrical circuit.

An ohmmeter is an instrument used to measure electrical resistance in ohms (Ω). It is a fundamental tool in electronics and electrical engineering, useful for diagnosing faults in circuits, checking the integrity of components, and verifying connections. ### Key Features of an Ohmmeter: - **Resistance Measurement**: It directly measures the resistance of resistive components, such as resistors, wiring, and other electronic components.

The residual-resistance ratio (RRR) is a measure used primarily in the field of superconductivity and materials science to assess the purity and quality of conductive materials, particularly metals. It is defined as the ratio of the resistivity of a material at room temperature (or a higher temperature) to the residual resistivity of that material as it approaches absolute zero temperature.

Resistance distance is a concept that arises in the field of graph theory and is related to electrical networks. It measures the "distance" between nodes in a graph based on the idea of resistance in an electrical circuit. Specifically, resistance distance is defined in terms of the effective resistance between two vertices in a graph when that graph is treated as an electrical network.

Sheet resistance is a measure of the resistance of a thin sheet of material, typically used to characterize thin films, conductive coatings, or semiconductor materials. It is an important parameter in fields such as electronics, materials science, and photovoltaics. Sheet resistance is denoted by the symbol \( R_s \) and is expressed in ohms per square (Ω/□).

Soil resistivity is a measure of how much a soil resists the flow of electric current. It is an important parameter in various engineering and environmental fields, particularly in electrical, geotechnical, and environmental engineering. Soil resistivity is influenced by several factors, including: 1. **Soil Composition**: The mineral composition and texture of the soil (sand, silt, clay) affect its ability to conduct electricity.

Spitzer resistivity refers to the electrical resistivity of a plasma, which is a state of matter composed of charged particles including ions and electrons. It is named after physicist Lyman Spitzer, who developed the concept in the context of astrophysics and plasma physics. In a plasma, the motion of charged particles can be influenced by electric and magnetic fields, and Spitzer resistivity provides a measure of how these charged particles collide with each other, leading to energy dissipation and resistance to flow.

Transconductance is an important parameter in the field of electronics, particularly in the study of amplifiers and other types of electronic circuits. It refers to the ratio of the output current of a device to the input voltage that causes it. Essentially, transconductance quantifies how effectively an input voltage can control the output current in a device like a transistor or an operational amplifier.

Variable-range hopping (VRH) is a transport mechanism commonly observed in disordered systems, such as insulators or semiconductors with localized electronic states. In these materials, charge carriers do not have enough energy to move freely, leading to a situation where conduction occurs through hopping between localized states rather than through band conduction. In VRH, the primary mechanism of charge transport involves the hopping of electrons (or holes) over varying distances, which can be influenced by the local energy landscape.