Name: factors that affect electrical resistance
Uploaded: 2023-04-30T12:39:00.000Z
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North Carolina K-12 Science Standard Course of Study

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Physical Science

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Motion and Stability- Forces and Interactions

PS.PSc.6.2

Resistance

Quando una corrente scorre attraverso un circuito, le collisioni tra elettroni e atomi nel filo provocano una resistenza al movimento degli elettroni, misurata in ohm.
La resistenza elettrica di un circuito è il rapporto tra la tensione applicata e la corrente che lo attraversa. La resistenza dipende anche dalla resistività del materiale ed è equivalente alla resistività del materiale moltiplicata per la lunghezza divisa per l'area della sezione trasversale del filo.
La temperatura influenza la resistenza dei materiali e può essere modellata utilizzando l'equazione della resistività.
Un componente di un circuito che riduce il flusso di corrente è noto come resistore, rappresentato da due simboli forniti dall'American National Standard Institute e dall'International Electrotechnical Commission.
Il carbonio è il materiale più comunemente utilizzato per realizzare i resistori. Le tracce in carbonio sono avvolte attorno a un nucleo in ceramica, che è collegato a due conduttori di rame e contrassegnato con quattro bande per identificare il resistore.
Le prime due bande colorate rappresentano le prime due cifre della resistenza, mentre il terzo e il quarto colore ne rappresentano il moltiplicatore e la tolleranza.

<ol>
	<li>OpenStax. (2019). Fisica universitaria Vol. 2. [Versione web], pp. 396-398. Estratto da <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>

resistenza

Quando una corrente attraversa qualsiasi conduttore, il conduttore causa un certo grado di difficoltà al flusso della corrente. La misura di tale difficoltà è nota come resistenza del materiale e viene rappresentata con R. Ogni materiale ha la propria resistenza. Nel caso dei conduttori, viene emesso calore ogni volta che una corrente li attraversa. La resistenza dipende dalla resistività del materiale. La resistività è una caratteristica del materiale utilizzato per fabbricare componenti elettrici, mentre la resistenza è una caratteristica del componente stesso.

Per calcolare la resistenza, si considera una sezione di filo conduttore con un'area trasversale di A, una lunghezza di L, e una resistività ρ. Una batteria è collegata attraverso il conduttore, fornendo una differenza di potenziale di ΔV attraverso di esso. La differenza di potenziale produce un campo elettrico che è proporzionale alla densità di corrente:

<img alt="Equation1" src="/files/ftp_upload/13747/13747_Equation_1.svg" style="text-align: center; height: 13px;" />

La magnitudine del campo elettrico attraverso un segmento del conduttore è uguale alla tensione divisa per la lunghezza, e la magnitudine della densità di corrente è uguale alla corrente divisa per l'area trasversale. Sostituendo i valori e ricordando che il campo elettrico è proporzionale alla resistività e alla densità di corrente, si può stabilire una relazione tra tensione e corrente:

<img alt="Equation2" src="/files/ftp_upload/13747/13747_Equation_2.svg" style="text-align: center; height: 26px;" />

La resistenza di un materiale può essere definita come il rapporto tra la tensione e la corrente che lo attraversa ed è rappresentata in ohm. La resistenza di un segmento cilindrico di un conduttore è uguale alla resistività del materiale moltiplicata per la lunghezza divisa per l'area:

<img alt="Equation3" src="/files/ftp_upload/13747/13747_Equation_3.svg" style="text-align: center; height: 26px;" />

La resistenza di un oggetto dipende anche dalla temperatura. Per un dato cilindro, se la lunghezza e l'area non cambiano notevolmente con la temperatura, la resistenza del materiale ha la stessa dipendenza dalla temperatura della resistività:

<img alt="Equation4" src="/files/ftp_upload/13747/13747_Equation_4.svg" style="text-align: center; height: 13px;" />

dove R0 è la resistenza originale a temperatura ambiente, R è la resistenza dopo una variazione di temperatura, e ɑ è il coefficiente di temperatura del materiale. <img height="20" src="file:///C:/Users/TIMOTH~1/AppData/Local/Temp/msohtmlclip1/01/clip_image006.gif" width="10" />

Resistenza

Quando una corrente si muove attraverso un conduttore, il conduttore causa un certo livello di difficoltà per il flusso della corrente. La misura di tale difficoltà è nota...

Education

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Unit 1

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Current and Resistance

Corrente e Resistenza

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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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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,...

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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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Factors That Affect Electrical Resistance

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