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

K12 Standards

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North Carolina K-12 Science Standard Course of Study

9-12

Physical Science

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Motion and Stability- Forces and Interactions

PS.PSc.6.2

Resistivity

المقاومة الكهربائية هي خاصية جوهرية للمادة ، تصف مدى فعالية مقاومتها لتدفق الشحنات.
المقاومة هي مقلوب التوصيل الكهربائي ويمكن تعريفها من حيث المجال الكهربائي وكثافة التيار. وحدة المقاومة في النظام الدولي للوحدات هي مقياس أوم.
الموصلات الجيدة لها موصلية عالية ولكن مقاومة منخفضة ، في حين أن العوازل الجيدة لها موصلية منخفضة ولكن مقاومة عالية.
تؤثر درجة الحرارة على مقاومة بعض المواد. في العديد من المواد ، يكون الاعتماد خطيا تقريبا ويمكن نمذجته باستخدام معادلة خطية حيث ρ هي مقاومة المادة عند درجة حرارة ، α هي معامل درجة حرارة المادة ، و ρ0 هي المقاومة في درجة حرارة الغرفة.
تزداد مقاومة بعض المواد ، مثل النحاس ، مع زيادة درجة الحرارة ؛ في حالات أخرى ، مثل الكربون ، تقل المقاومة مع زيادة درجة الحرارة.
في أشباه الموصلات ، يكون معامل درجة الحرارة سالبا ، مما يعني أن المقاومة تنخفض مع زيادة درجة الحرارة.

<ol>
	<li>OpenStax. (2019). جامعة الفيزياء المجلد 2. [نسخة الويب] ، الصفحة 396 - 398. تم الاسترجاع من <a href="https://openstax.org/books/university-physics-volume-2/pages/9-3-resistivity-and-resistance">https://openstax.org/books/university-physics-volume-2/pages/9-3-resistivity-and-resistance</a></li>
</ol>

المقاومة النوعية

<div style="direction:rtl">عند تطبيق جهد على موصل، يتولد مجال كهربائي، وتشعر الشحنات الموجودة في الموصل بالقوة الناتجة عن المجال الكهربائي. تعتمد الكثافة الحالية الناتجة على المجال الكهربائي وخصائص المادة. في بعض المواد، بما في ذلك المعادن عند درجة حرارة معينة، تكون كثافة التيار متناسبة تقريبًا مع المجال الكهربائي. في هذه الحالات، يمكن نمذجة الكثافة الحالية على النحو التالي: <img alt="Equation1" src="/files/ftp_upload/13746/13746_Equation_1.svg" style="text-align: center; height: 16px;"> حيث σ هي الموصلية الكهربائية ويمثلها (Ω·m)−1. تشبه الموصلية الكهربائية التوصيل الحراري وهي مقياس لقدرة المادة على توصيل أو نقل الكهرباء. الموصلات لديها الموصلية الكهربائية أعلى من العوازل. الموصلية هي خاصية جوهرية للمادة. خاصية جوهرية أخرى للمادة هي مقاومتها، أو المقاومة الكهربائية. إن مقاومة المادة هي مقياس لمدى قوة مقاومة المادة لتدفق التيار الكهربائي. يمكن التعبير عن المقاومة على أنها معكوس التوصيل الكهربائي ويرمز لها بالحرف اليوناني rho، ρ. وحدة المقاومة في وحدات SI هي الأوم متر. يمكن أيضًا تعريف المقاومة على أنها نسبة المجال الكهربائي إلى كثافة التيار. كلما زادت المقاومة، كلما زاد المجال اللازم لإنتاج كثافة تيار معينة. كلما انخفضت المقاومة، زادت كثافة التيار الناتج عن مجال كهربائي معين. كما هو موضح في الجدول 1، جيد  تظهر الموصلات موصلية عالية ومقاومة منخفضة، بينما تظهر العوازل الجيدة موصلية منخفضة ومقاومة عالية. الجدول 1: يسرد قيم المقاومة والتوصيل لمختلف المواد. <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;">المواد</td> <td style="color: black; border: 1px solid black; text-align: center;">الموصلية، σ ( Ω · م)−1</td> <td style="color: black; border: 1px solid black; text-align: center;">المقاومة، ρ ( Ω · م)</td> <td style="color: black; border: 1px solid black; text-align: center;">درجة الحرارة المعامل، α (°C)−1</td> </tr> <tr> <td style="color: black; border: 1px solid black; text-align: center;">فضي</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;">نحاس</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;">ذهبي</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;">ألومنيوم</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;">تنغستن</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;">كربون (نقي)</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;">سيليكون</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;">كهرماني</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;">زجاج</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;">لوسيت</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></div>

عندما يتم تطبيق جهد على موصل ، يتم إنشاء مجال كهربائي ، وتشعر الشحنات في الموصل بالقوة الناتجة عن المجال الكهربائي. ال...

Education

JoVE Core

Physics

الفيزياء

Unit 1

الوحدة الأولى

Current and Resistance

التيار والمقاومة

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

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...

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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

Diode Current and Reverse Bias

A diode is a nonohmic circuit element that makes current and voltage behave differently from Ohm’s law. In most substances, current is proportional to the voltage applied, but a diode does not show a linear current-voltage relationship. A diode is a semiconducting device with two terminals: an anode, which is the positive terminal, and a cathode, which is the negative terminal. It allows current to flow in only one direction. In a simple circuit with a battery, a diode, and a resistor, the...

electrical power

Power Limits in Electrical Circuits

Electrical power in a circuit depends on current and voltage. It is the product of these two values and is measured in watts, or joules per second. That relationship helps explain how much energy a circuit can deliver. A car’s auxiliary power outlet is one real-world example. Some outlets are rated at 20 amps and 12 volts, so they can deliver a maximum of 240 watts. That rating shows the upper limit of power the circuit can provide to devices such as a cell phone charger. Bulb wattage also...

electrical energy

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Electrical energy is the energy transferred when electrons move from one point to another. The longer an appliance is used, the more electrical energy it consumes. If power stays constant, electrical energy equals the power used by the device times the time it runs. That is why longer use leads to a higher electric bill. Electric bills measure this energy in kilowatt-hours. One kilowatt-hour is equal to 3.6 × 10^6 joules. You can lower electrical energy use by cutting the time an appliance...

continuity equation

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boundary conditions for current density

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Current density at a boundary changes when two conducting materials have different electrical conductivities. The normal component of current density stays continuous across the interface. The tangential component, which runs along the surface, becomes discontinuous across the boundary. Consider two conducting media with conductivities σ1 and σ2 separated by an interface. At point P1 in medium 1, the steady current density makes an angle α1 with the normal. At point P2 in medium 2, the current...

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...

theory of metallic conduction

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

physics

JoVE Core Physics introduces the theory and application of fundamental physics topics, including kinematics, dynamics, fluid mechanics, statics, waves, and acoustics, with concise and easy-to-understand animated videos. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide.

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Waves and Their Applications in Technologies for Information Transfer

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New York State Science Learning Standards

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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

Electrical current is defined as the rate at which charge flows. When there is a large current present, such as that used to run a refrigerator, a large ...

Drift Velocity

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Current Density

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Resistance

When a current moves through any conductor, the conductor causes some level of difficulty for the current to flow. The measure of that difficulty is known ...

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

The total amount of current flowing per unit cross-sectional area is called the current density. Hence, the current passing through a cross-sectional area ...

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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Obtain, evaluate, and communicate information to explain how current is affected by changes in composition, length, temperature, and diameter of wire.

Magnetism

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Magnetic Fields

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Magnetic Field Lines

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Magnetic Flux

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motion-of-a-charged-particle-in-a-magnetic-field

Motion Of A Charged Particle In A Magnetic Field

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Magnetic Force On A Current-Carrying Conductor

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magnetic-force-on-current-carrying-wires-example

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Force On A Current Loop In A Magnetic Field

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Magnetic Field Of A Current Loop

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Divergence and Curl of Magnetic Field

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To evaluate the divergence of the ...

Ampere's Law

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Ampere's Law: Problem-Solving

Ampere&#x27;s law states that for any closed looped path, the line integral of the magnetic field along the path equals the vacuum permeability times the ...

Solenoids

A solenoid is a conducting wire coated with an insulating material, wound tightly in the form of a helical coil. The magnetic field for a solenoid is the ...

Magnetic Field of a Solenoid

A solenoid is a conducting wire coated with an insulating material, wound tightly in the form of a helical coil. The magnetic field due to a solenoid is ...

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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