Name: resistivity in conductors and insulators
Uploaded: 2023-04-30T12:38:52.000Z
Duration: 1 min 22 s
Channel: JoVE

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Resistivity

Electrical resistivity is an intrinsic property of a material, describing how effectively it resists the flow of charges.
Resistivity is the reciprocal of electrical conductivity and can be defined in terms of the electrical field and the current density. The SI unit of resistivity is the ohm-meter.
Good conductors have a high conductivity but a low resistivity, whereas good insulators have a low conductivity but a high resistivity.
Temperature influences the resistivity of some materials. In many materials, the dependence is approximately linear and can be modeled using a linear equation where &#961; is the resistivity of the material at a temperature, &#945; is the temperature coefficient of the material, and &#961;0 is the resistivity at room temperature.
The resistivity of some materials, such as copper, increases as temperature increases; in others, like carbon, resistivity decreases as temperature increases.
In semiconductors, the temperature coefficient is negative, implying that resistivity decreases as temperature increases.

weerstand

Wanneer er spanning wordt toegepast op een geleider, wordt er een elektrisch veld gegenereerd en voelen de ladingen in de geleider de kracht als gevolg van het elektrische veld. De stroomdichtheid die hierdoor ontstaat, is afhankelijk van het elektrische veld en de eigenschappen van het materiaal. In sommige materialen, inclusief metalen bij een bepaalde temperatuur, is de stroomdichtheid ongeveer evenredig met het elektrische veld. In deze gevallen kan de stroomdichtheid als volgt worden gemodelleerd: <img alt="Equation1" src="/files/ftp_upload/13746/13746_Equation_1.svg" style="text-align: center; height: 16px;"> waarbij σ de elektrische geleidbaarheid is en wordt weergegeven door (Ω·m)−1. Elektrische geleidbaarheid is analoog aan thermische geleidbaarheid en is een maatstaf voor het vermogen van een materiaal om elektriciteit te geleiden of over te brengen. Geleiders hebben een hogere elektrische geleidbaarheid dan isolatoren. Geleidbaarheid is een intrinsieke eigenschap van een materiaal. Een andere intrinsieke eigenschap van een materiaal is de soortelijke weerstand, of elektrische weerstand. De soortelijke weerstand van een materiaal is een maatstaf voor hoe sterk een materiaal de stroom van elektrische stroom tegenwerkt. Weerstand kan worden uitgedrukt als het omgekeerde van elektrische geleidbaarheid en wordt weergegeven door de Griekse letter rho, ρ. De eenheid van soortelijke weerstand in SI-eenheden is de ohm-meter. Weerstand kan ook worden gedefinieerd als de verhouding tussen het elektrische veld en de stroomdichtheid. Hoe groter de soortelijke weerstand, hoe groter het veld dat nodig is om een bepaalde stroomdichtheid te produceren. Hoe lager de soortelijke weerstand, hoe groter de stroomdichtheid die door een bepaald elektrisch veld wordt geproduceerd. Zoals vermeld in Tabel 1, is goed geleiders vertonen een hoge geleidbaarheid en een lage weerstand, terwijl goede isolatoren een lage geleidbaarheid en een hoge weerstand vertonen. Tabel 1: geeft een overzicht van de weerstands- en geleidbaarheidswaarden voor verschillende materialen. <table style="margin-left: auto; margin-right: auto;"> <tbody style="border: 1px solid black;"> <tr> <td style="color: black; border: 1px solid black; text-align: center;">Materialen</td> <td style="color: black; border: 1px solid black; text-align: center;">Geleidbaarheid, σ ( Ω · m)−1</td> <td style="color: black; border: 1px solid black; text-align: center;">Weerstand, ρ ( Ω · m)</td> <td style="color: black; border: 1px solid black; text-align: center;">Temperatuur Coëfficiënt, α (°C)−1</td> </tr> <tr> <td style="color: black; border: 1px solid black; text-align: center;">Zilver</td> <td style="color: black; border: 1px solid black; text-align: center;">6,29 × 107</td> <td style="color: black; border: 1px solid black; text-align: center;">1,59 × 10−8</td> <td style="color: black; border: 1px solid black; text-align: center;">0,0038</td> </tr> <tr> <td style="color: black; border: 1px solid black; text-align: center;">Koper</td> <td style="color: black; border: 1px solid black; text-align: center;">5,95 × 107</td> <td style="color: black; border: 1px solid black; text-align: center;">1,68 × 10−8</td> <td style="color: black; border: 1px solid black; text-align: center;">0,0039</td> </tr> <tr> <td style="color: black; border: 1px solid black; text-align: center;">Goud</td> <td style="color: black; border: 1px solid black; text-align: center;">4.10 × 107</td> <td style="color: black; border: 1px solid black; text-align: center;">2,44 × 10−8</td> <td style="color: black; border: 1px solid black; text-align: center;">0,0034</td> </tr> <tr> <td style="color: black; border: 1px solid black; text-align: center;">Aluminium</td> <td style="color: black; border: 1px solid black; text-align: center;">3,77 × 107</td> <td style="color: black; border: 1px solid black; text-align: center;">2,65 × 10−8</td> <td style="color: black; border: 1px solid black; text-align: center;">0,0039</td> </tr> <tr> <td style="color: black; border: 1px solid black; text-align: center;">Tungsten</td> <td style="color: black; border: 1px solid black; text-align: center;">1,79 × 107</td> <td style="color: black; border: 1px solid black; text-align: center;">5,60 × 10−8</td> <td style="color: black; border: 1px solid black; text-align: center;">0,0045</td> </tr> <tr> <td style="color: black; border: 1px solid black; text-align: center;">Koolstof (puur)</td> <td style="color: black; border: 1px solid black; text-align: center;">2,86 × 10−6 </td> <td style="color: black; border: 1px solid black; text-align: center;">3,50 × 10−5 </td> <td style="color: black; border: 1px solid black; text-align: center;">−0.0005</td> </tr> <tr> <td style="color: black; border: 1px solid black; text-align: center;">Silicium</td> <td style="color: black; border: 1px solid black; text-align: center;"></td> <td style="color: black; border: 1px solid black; text-align: center;"> 0.1 − 2300</td> <td style="color: black; border: 1px solid black; text-align: center;">−0.07</td> </tr> <tr> <td style="color: black; border: 1px solid black; text-align: center;">Amber</td> <td style="color: black; border: 1px solid black; text-align: center;">2,00 × 10−15 </td> <td style="color: black; border: 1px solid black; text-align: center;">5 × 1014</td> <td style="color: black; border: 1px solid black; text-align: center;"></td> </tr> <tr> <td style="color: black; border: 1px solid black; text-align: center;">Glas</td> <td style="color: black; border: 1px solid black; text-align: center;">10−9 − 10−14</td> <td style="color: black; border: 1px solid black; text-align: center;">109 − 1014</td> <td style="color: black; border: 1px solid black; text-align: center;"></td> </tr> <tr> <td style="color: black; border: 1px solid black; text-align: center;">Lucite</td> <td style="color: black; border: 1px solid black; text-align: center;"><10−13 </td> <td style="color: black; border: 1px solid black; text-align: center;">>1013</td> <td style="color: black; border: 1px solid black; text-align: center;"></td> </tr> </tbody> </table>

Weerstand

When a voltage is applied to a conductor, an electrical field is generated, and charges in the conductor feel the force due to the electrical field. The ...

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resistivity in conductors and insulators

Resistivity describes how much a material opposes electric current. When a voltage is applied to a conductor, an electric field forms. The charges in the conductor feel that force, and a current density develops. In some materials, including metals at a given temperature, the current density is approximately proportional to the electric field.

In those cases, current density can be modeled with conductivity, written as sigma. Electrical conductivity is measured in (ohm·m)^−1. It tells how well a material can conduct electricity. This idea is similar to thermal conductivity, which describes how well a material carries heat. Conductors have higher electrical conductivity than insulators, and conductivity is an intrinsic property of the material.

Resistivity, written as rho, is another intrinsic property. It is the reciprocal of electrical conductivity. In SI units, resistivity is measured in ohm-meter. It can also be defined as the ratio of electric field to current density. A higher resistivity means a larger electric field is needed to produce a given current density. A lower resistivity means the same electric field produces a larger current density.

The transcript also compares common materials. Good conductors have high conductivity and low resistivity. Good insulators have low conductivity and high resistivity. Examples of good conductors include silver, copper, gold, aluminum, and tungsten. Pure carbon has much lower conductivity than these metals. Silicon falls between conductor and insulator values, while amber, glass, and Lucite show very high resistivity and very low conductivity.

Resistivity in Conductors and Insulators

electrical current

Current Flow in Simple Circuits

Electrical current is the flow of charge in a circuit. A large current means a large amount of charge moves through a wire in a short time. A small current means only a small amount of charge moves through the circuit over a longer time. Examples include the current needed to run a refrigerator and the smaller current used by a handheld calculator. The SI unit for current is the ampere, or amp. It is named for the French physicist André-Marie Ampère (1775–1836). One ampere means one coulomb of...

drift velocity

Electrical Current and Electron Drift

Electrical current in a conductor depends on moving charges and the tiny drift speed of those charges. When a free charge enters a wire, it pushes nearby charges ahead because like charges repel each other. That push spreads through the material very quickly, so the electrical signal moves through the system at nearly the speed of light. This fast signal is not the same as the slow motion of each charge. It is a rapidly spreading change in the electric field, often described as an electrical...

current density

Current Density in Wires and Solutions

Current density describes how much electric current passes through a given cross-sectional area. It helps show not just the size of the current, but also how it is distributed through a conductor. The current density can change from point to point because the local charge flow can vary. If the current flow is uniform, the amount of current is the same at every point along the conductor, even when the conductor’s area changes. Current density is measured in amperes per square meter. Its...

resistivity

Resistivity describes how much a material opposes electric current. When a voltage is applied to a conductor, an electric field forms. The charges in the conductor feel that force, and a current density develops. In some materials, including metals at a given temperature, the current density is approximately proportional to the electric field. In those cases, current density can be modeled with conductivity, written as sigma. Electrical conductivity is measured in (ohm·m)^−1. It tells how well...

resistance

Factors That Affect Electrical Resistance

Electrical resistance describes how much a conductor opposes the flow of current. It is represented by R. When current passes through a conductor, heat is also produced. Resistance is tied to the material’s resistivity, which is a property of the material used to make an electrical component. Resistance is different from resistivity. Resistivity belongs to the material itself, while resistance belongs to the finished component. To study this relationship, consider a wire with length L,...

ohm's law

Measuring Current, Voltage, and Resistance

Ohm's law describes the relationship between current, voltage, and resistance in many materials. In these cases, the current through a substance is directly proportional to the voltage applied to it. The idea was first shown experimentally by German physicist Georg Simon Ohm, who studied current in a metal wire. A material, component, or device that follows this pattern is called ohmic. An ohmic component has a current that increases in step with voltage. A material or component that does not...

non-ohmic devices

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electrical conductivity

Resistance and Ohm's Law in Conductors

Resistance and Ohm's law help explain how electric current moves through a conductor. In a perfect conductor, the electric field inside is zero because free electrons move to cancel it. Any extra charge then stays on the surface. In a practical conductor, an applied electric field can remain in place. That field drives electrons through the material and creates a current. The current density, which is current per unit area, is related to the electric field. More generally, it is related to the...

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Electron Drift in Metallic Conduction

Electron drift in metallic conduction explains how free electrons move through a conductor. A classical model can describe this motion closely, even though quantum mechanics gives the best overall picture. This model is called the theory of metallic conduction. In this theory, Newton's second law is used to find the acceleration of an electron when an electric field is applied. The electron's velocity is then found from that acceleration. The electron travels through a crystal of positive ions...

key terms and concepts

Learn how resistivity relates to conductivity, electric fields, and current density. See why conductors and insulators behave differently in common materials.

Resistivity in Conductors and Insulators | JoVE K12

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Position and Displacement

The position of an object defines its location relative to a convenient frame of reference at any particular time. A frame of reference is an arbitrary ...

Average Velocity

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Instantaneous Velocity - I

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Instantaneous Velocity - II

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PS.PSc.4.1

Electrical Current

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Drift Velocity

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Current Density

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Resistance

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Ohm's Law

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Non-ohmic Devices

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Construct an explanation to compare simple series and parallel circuits in terms of Ohm's Law.

Continuity Equation

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Boundary Conditions for Current Density

Current density becomes discontinuous across an interface of materials with different electrical conductivities. The normal component of the current ...

Electrical Conductivity

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Theory of Metallic Conduction

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Solenoids

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Magnetic Field of a Solenoid

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Toroids

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Use models to explain magnetism in terms of domains, interactions of poles, and magnetic fields.

PS.PSc.6.4

Analyze motion in terms of speed, velocity, acceleration, and momentum.

Resistivity in Conductors and Insulators

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