Name: factors that affect electrical resistance
Uploaded: 2023-04-30T12:39:00.000Z
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Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Physical Science

motion-and-stability-forces-and-interactions

Motion and Stability- Forces and Interactions

PS.PSc.6.2

Resistance

عندما يتدفق التيار عبر دائرة كهربائية ، فإن الاصطدامات بين الإلكترونات والذرات في السلك تسبب مقاومة لحركة الإلكترونات ، تقاس بالأوم.
المقاومة الكهربائية للدائرة هي نسبة الجهد المطبق إلى التيار المتدفق عبرها. تعتمد المقاومة أيضا على مقاومة المادة وهي تعادل مقاومة المادة مضروبا في الطول مقسوما على مساحة المقطع العرضي للسلك.
تؤثر درجة الحرارة على مقاومة المواد ويمكن نمذجتها باستخدام معادلة المقاومة.
يعرف أحد المكونات الموجودة في الدائرة التي تقلل من تدفق التيار باسم المقاوم ، ويمثله رمزان يوفرهما المعهد الوطني الأمريكي للمعايير واللجنة الكهروتقنية الدولية.
الكربون هو المادة الأكثر شيوعا المستخدمة في صنع المقاومات. يتم لف مسارات الكربون حول قلب خزفي ، متصل بسلك نحاسي ومميز بأربعة نطاقات لتحديد المقاوم.
يمثل الشريطان الملونان الأولان أول رقمين من المقاومة ، بينما يمثل اللونان الثالث والرابع مضاعفها وتسامحها.

<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>

مقاومة

<div style="direction:rtl">عندما يتحرك تيار عبر أي موصل، يسبب الموصل مستوى معين من الصعوبة في تدفق التيار. يُعرف مقياس هذه الصعوبة بمقاومة المادة ويمثلها R. كل مادة لها مقاومتها الخاصة. وفي حالة الموصلات، تنبعث الحرارة كلما مر تيار من خلالها. تعتمد المقاومة على مقاومة المادة. المقاومة هي سمة من سمات المادة المستخدمة لتصنيع المكونات الكهربائية، في حين أن المقاومة هي سمة من سمات المكون نفسه. لحساب المقاومة، فكر في مقطع من سلك موصل بمساحة مقطع عرضي A، وطول L، ومقاومته ρ. يتم توصيل بطارية عبر الموصل، مما يوفر فرق جهد قدره ΔV عبره. وينتج عن فرق الجهد مجال كهربائي يتناسب مع كثافة التيار: <img alt="Equation1" src="/files/ftp_upload/13747/13747_Equation_1.svg" style="text-align: center; height: 13px;"> إن حجم المجال الكهربائي عبر مقطع من الموصل يساوي الجهد مقسومًا على الطول، وحجم كثافة التيار يساوي التيار مقسومًا على مساحة المقطع العرضي. من خلال استبدال القيم والتذكير بأن المجال الكهربائي يتناسب مع المقاومة وكثافة التيار، يمكن إنشاء علاقة بين الجهد والتيار: <img alt="Equation2" src="/files/ftp_upload/13747/13747_Equation_2.svg" style="text-align: center; height: 26px;"> يمكن تعريف مقاومة المادة على أنها نسبة الجهد إلى التيار الذي يمر عبرها ويتم تمثيلها بالأوم. مقاومة القطعة الأسطوانية للموصل تساوي مقاومة المادة مضروبة في الطول مقسومًا على المساحة: <img alt="Equation3" src="/files/ftp_upload/13747/13747_Equation_3.svg" style="text-align: center; height: 26px;"> تعتمد مقاومة الجسم أيضًا على درجة الحرارة. بالنسبة لأسطوانة معينة، إذا لم يتغير الطول والمساحة بشكل كبير مع درجة الحرارة، فإن مقاومة المادة لها نفس درجة الحرارة التي تعتمد عليها المقاومة: <img alt="Equation4" src="/files/ftp_upload/13747/13747_Equation_4.svg" style="text-align: center; height: 13px;"> حيث R0  هي المقاومة الأصلية عند درجة حرارة الغرفة، R هي المقاومة بعد تغير درجة الحرارة، وɑ هو معامل درجة حرارة المادة.<img height="20" src="file:///C:/Users/TIMOTH~1/AppData/Local/Temp/msohtmlclip1/01/clip_image006.gif" width="10"></div>

عندما يتحرك التيار عبر أي موصل ، يتسبب الموصل في مستوى معين من صعوبة تدفق التيار. مقياس هذه الصعوبة معروف ...

Education

JoVE Core

Physics

الفيزياء

Unit 1

الوحدة الأولى

Current and Resistance

التيار والمقاومة

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

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, cross-sectional area A, and resistivity ρ. If a battery provides a potential difference ΔV across the wire, the voltage creates an electric field in the conductor.

The electric field across the wire segment equals the voltage divided by the length. The current density equals the current divided by the cross-sectional area. Because the electric field is proportional to resistivity and current density, these values can be combined to relate voltage and current. Resistance is then defined as the ratio of voltage to current and is measured in ohms.

For a cylindrical conductor, resistance equals resistivity multiplied by length divided by area. Resistance also changes with temperature. If the length and area stay nearly the same as temperature changes, the resistance follows the same temperature dependence as the resistivity. In that case, R0 is the original resistance at room temperature, R is the resistance after the temperature change, and α is the temperature coefficient of the material.

Factors That Affect Electrical Resistance

factors-that-affect-electrical-resistance

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 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...

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

Cutting Electric Bills with Efficient Lighting

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

Charge Conservation and Current Flow

Charge conservation and current flow are linked through the continuity equation. The current density is the amount of current flowing per unit cross-sectional area. The current through a surface can be written as a surface integral of the current density. The conservation of charge says that the total current leaving a volume equals the rate at which charge inside that volume decreases. The total charge can be written using volume charge density, which is a space function. Because of this, the...

boundary conditions for current density

Current Density at Conductivity Boundaries

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 resistance depends on resistivity, wire length, cross-sectional area, voltage, current, and temperature in conductors and electrical circuits.

Factors That Affect Electrical Resistance | 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.

PS.PSc.6.3

PS.Phy.4.3

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Energy And Waves

Electricity

Electricity And Magnetism

DC circuits

Tennessee Academic Standards

High School

Energy

PHYS.PS3.11

Virginia  Standards of Learning

HIgh School

PS.9

PS.9.b

PS.9.c

PH.8

PH.8.b

Arizona Science Standards

HS+Phy.P4

HS+Phy.P4U1.8

Alabama Course of Study Science

waves-and-their-applications-in-technologies-for-information-transfer

Waves and Their Applications in Technologies for Information Transfer

9-12.PS.2.3.c

9-12.PS.2.3.d

9-12.P.2.6.b

9-12.P.2.6.d

Florida Department of Education

SC.912.P.10

SC.912.P.10.15

Texas Essential Knowledge and Skills

PHYS.6

PHYS.6.D

PHYS.6.E

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Energy

HS-PS3-6.

Georgia Standards of Excellence

SPS10.

Understanding Electrical Quantities

SP5.

Ohm’s Law

Position and Displacement

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Average Velocity

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Instantaneous Velocity - I

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Instantaneous Velocity - II

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Average Acceleration

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average-and-instantaneous-velocity-vectors

Average and Instantaneous Velocity Vectors

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Acceleration Vectors

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Analyze and interpret data to explain the motion of an object moving with a constant velocity or that is accelerating.

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

The high speed of electrical signals results from the fact that the force between charges acts rapidly at a distance. Thus, when a free charge is forced ...

Current Density

The total amount of current flowing through one unit value of a cross-sectional area is referred to as current density. If the current flow is uniform, ...

Resistivity

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 ...

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

In most substances, the current flow is proportional to the voltage applied to it. A simple relationship between the values of current, voltage, and ...

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

In perfect conductors, the electric field inside is always zero due to the abundance of free electrons, which nullify any field by flowing. As a result, ...

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

The representation of magnetic fields by magnetic field lines is very useful in visualizing the strength and direction of the magnetic field. Each of the ...

Magnetic Flux

The magnetic flux measures the number of magnetic field lines passing through a given surface area. The SI unit for magnetic flux is the weber (Wb). ...

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

Motion Of A Charged Particle In A Magnetic Field

A charged particle experiences a force when moving through a magnetic field. Consider the field to be uniform and the charged particle to move ...

Magnetic Force

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magnetic-force-on-a-current-carrying-conductor

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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Torque On A Current Loop In A Magnetic Field

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Biot-Savart Law

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Biot-Savart Law: Problem-Solving

The magnitude and direction of a magnetic field created by a steady current can be calculated using the Biot-Savart law.
Consider a mobile phone battery ...

Magnetic Field Due to Two Straight Wires

Consider two parallel straight wires carrying a current of 10 A and 20 A in the same direction and separated by a distance of 20 cm. Calculate the ...

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.

Factors That Affect Electrical Resistance

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