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

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.

weerstand

Wanneer een stroom door een geleider beweegt, veroorzaakt de geleider een bepaalde moeilijkheidsgraad voor het vloeien van de stroom. De maatstaf voor die moeilijkheid staat bekend als de weerstand van het materiaal en wordt weergegeven door R. Ieder materiaal heeft zijn eigen weerstand. In het geval van geleiders wordt warmte afgegeven wanneer er stroom doorheen gaat. Weerstand hangt af van de soortelijke weerstand van het materiaal. Weerstand is een kenmerk van het materiaal dat wordt gebruikt om elektrische componenten te vervaardigen, terwijl de weerstand een kenmerk is van het onderdeel zelf. Om de weerstand te berekenen, neem je een stuk geleidende draad in overweging met een dwarsdoorsnede van A, een lengte van L en een soortelijke weerstand 's Δ. Over de geleider is een batterij aangesloten, waardoor er een potentiaalverschil van ΔV over ontstaat. Het potentiaalverschil produceert een elektrisch veld dat evenredig is met de stroomdichtheid: <img alt="Equation1" src="/files/ftp_upload/13747/13747_Equation_1.svg" style="text-align: center; height: 13px;"> De grootte van het elektrische veld over een segment van de geleider is gelijk aan de spanning gedeeld door de lengte, en de grootte van de stroomdichtheid is gelijk aan de stroom gedeeld door het dwarsdoorsnedeoppervlak. Door de waarden te vervangen en eraan te herinneren dat het elektrische veld evenredig is met de weerstand en de stroomdichtheid, kan een verband tussen spanning en stroom worden vastgesteld: <img alt="Equation2" src="/files/ftp_upload/13747/13747_Equation_2.svg" style="text-align: center; height: 26px;"> De weerstand van een materiaal kan worden gedefinieerd als de verhouding tussen de spanning en de stroom die er doorheen gaat, en wordt weergegeven in ohm. De weerstand van een cilindrisch segment van een geleider is gelijk aan de soortelijke weerstand van het materiaal vermenigvuldigd met de lengte gedeeld door de oppervlakte: <img alt="Equation3" src="/files/ftp_upload/13747/13747_Equation_3.svg" style="text-align: center; height: 26px;"> De weerstand van een object is ook afhankelijk van de temperatuur. Als voor een bepaalde cilinder de lengte en het oppervlak niet sterk veranderen met de temperatuur, heeft de weerstand van het materiaal dezelfde temperatuurafhankelijkheid als de soortelijke weerstand: <img alt="Equation4" src="/files/ftp_upload/13747/13747_Equation_4.svg" style="text-align: center; height: 13px;"> waarbij R0 de oorspronkelijke weerstand bij kamertemperatuur is, R de weerstand is na een temperatuurverandering, en ɑ is de temperatuurcoëfficiënt van het materiaal.<img height="20" src="file:///C:/Users/TIMOTH~1/AppData/Local/Temp/msohtmlclip1/01/clip_image006.gif" width="10">

Weerstand

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

JoVE Core

Physics

Natuurkunde

Unit 1

Onderdeel 1

Current and Resistance

Stroom en Weerstand

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

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...

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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...

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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...

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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

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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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Ohio’s Learning Standards and Model Curriculum

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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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Understanding Electrical Quantities

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Ohm’s Law

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Factors That Affect Electrical Resistance

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