Name: factors that affect electrical resistance
Uploaded: 2023-04-30T12:39:00.000Z
Duration: 1 min 19 s
Channel: JoVE

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Physical Science

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Resistance

When a current flows through a circuit, the collisions between electrons and atoms in the wire causes resistance to the electrons&#39; motion, measured in ohms.
A circuit&#39;s electrical resistance is the ratio of applied voltage to the current flowing through it. Resistance also depends on the material&#39;s resistivity and is equivalent to the resistivity of the material times the length divided by the cross-sectional area of the wire.
Temperature influences the resistance of materials and can be modeled using the resistivity equation.
A component in a circuit that reduces the current flow is known as a resistor, represented by two symbols provided by the American National Standard Institute and the International Electrotechnical Commission.
Carbon is the most common material used to make resistors. The carbon tracks are wrapped around a ceramic core, which is connected to two copper leads and marked with four bands to identify the resistor.
The first two colored bands represent the first two digits of the resistance, while the third and fourth colors represent its multiplier and tolerance.

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 as the resistance of the material and is represented by R. Every material has its own resistance. In the case of conductors, heat is emitted whenever a current passes through them. Resistance depends on the resistivity of the material. Resistivity is a characteristic of the material used to fabricate electrical components, whereas the resistance is a characteristic of the component itself.
To calculate the resistance, consider a section of conducting wire with a cross-sectional area of A, a length of L, and a resistivity ρ. A battery is connected across the conductor, providing a potential difference of ΔV across it. The potential difference produces an electrical field that is proportional to the current density:
<img alt="Electrical field equation, E=ρJ, formula for current density, used in electromagnetic studies." src="/files/ftp_upload/13747/13747_Equation_1.svg" style="text-align: center; height: 13px;" data-altupdatedat="1761830439000" data-alt="Equation1">
The magnitude of the electrical field across a segment of the conductor is equal to the voltage divided by the length, and the magnitude of the current density is equal to the current divided by the cross-sectional area. By substituting the values and recalling that the electrical field is proportional to the resistivity and the current density, a relation between voltage and current can be established:
<img alt="Ohm's Law formula, V/L=ρI/A, illustrating electrical resistance principles." src="/files/ftp_upload/13747/13747_Equation_2.svg" style="text-align: center; height: 26px;" data-altupdatedat="1761830439000" data-alt="Equation2">
The resistance of a material can be defined as the ratio of the voltage to the current passing through it and is represented in ohms. The resistance of a cylindrical segment of a conductor is equal to the resistivity of the material multiplied by the length divided by the area:
<img alt="Ohm's Law formula R=V/I=ρL/A, electrical resistance, diagram." src="/files/ftp_upload/13747/13747_Equation_3.svg" style="text-align: center; height: 26px;" data-altupdatedat="1761830439000" data-alt="Equation3">
The resistance of an object also depends on the temperature. For a given cylinder, if the length and area do not change greatly with temperature, the resistance of the material has the same temperature dependence as the resistivity:
<img alt="Static equilibrium formula \(R = R_0(1 + \alpha \Delta T)\), equation, temperature dependence." src="/files/ftp_upload/13747/13747_Equation_4.svg" style="text-align: center; height: 13px;" data-altupdatedat="1761830439000" data-alt="Equation4">
where R0 is the original resistance at room temperature, R is the resistance after a temperature change, and ɑ is the temperature coefficient of the material.<img height="20" src="file:///C:/Users/TIMOTH~1/AppData/Local/Temp/msohtmlclip1/01/clip_image006.gif" width="10">

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 ...

Education

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Physics

Unit 1

Current and Resistance

KEY TERMS AND CONCEPTS

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

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resistivity

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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...

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

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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

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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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Factors That Affect Electrical Resistance

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