Name: resistivity in conductors and insulators
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Resistivity

A resistividade elétrica é uma propriedade intrínseca de um material, descrevendo a eficácia com que ele resiste ao fluxo de cargas.
A resistividade é o recíproco da condutividade elétrica e pode ser definida em termos do campo elétrico e da densidade de corrente. A unidade SI de resistividade é o ohmímetro.
Bons condutores têm alta condutividade, mas baixa resistividade, enquanto bons isoladores têm baixa condutividade, mas alta resistividade.
A temperatura influencia a resistividade de alguns materiais. Em muitos materiais, a dependência é aproximadamente linear e pode ser modelada usando uma equação linear onde ρ é a resistividade do material a uma temperatura, α é o coeficiente de temperatura do material e ρ0 é a resistividade à temperatura ambiente.
A resistividade de alguns materiais, como o cobre, aumenta à medida que a temperatura aumenta; em outros, como o carbono, a resistividade diminui à medida que a temperatura aumenta.
Em semicondutores, o coeficiente de temperatura é negativo, o que implica que a resistividade diminui à medida que a temperatura aumenta.

<ol>
	<li>OpenStax. (2019). Física Universitária Vol. 2. [Versão Web], Pg 396 - 398. Obtido de <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>

resistividade

Quando uma voltagem é aplicada a um condutor, um campo elétrico é gerado, e as cargas no condutor sentem a força devido ao campo elétrico. A densidade de corrente resultante depende do campo elétrico e das propriedades do material. Em alguns materiais, incluindo metais em uma determinada temperatura, a densidade de corrente é aproximadamente proporcional ao campo elétrico. Nesses casos, a densidade de corrente pode ser modelada como: :

<img alt="Equation1" src="/files/ftp_upload/13746/13746_Equation_1.svg" style="text-align: center; height: 16px;" />

onde σ é a condutividade elétrica e é representada por (Ω·m)⁻¹. A condutividade elétrica é análoga à condutividade térmica e é uma medida da capacidade de um material de conduzir ou transmitir eletricidade. Os condutores têm uma condutividade elétrica maior do que os isolantes. A condutividade é uma propriedade intrínseca de um material. Outra propriedade intrínseca de um material é sua resistividade, ou resistividade elétrica. A resistividade de um material é uma medida de quão fortemente um material se opõe ao fluxo de corrente elétrica. A resistividade pode ser expressa como o recíproco da condutividade elétrica e é representada pela letra grega rho, ρ. A unidade de resistividade em unidades do SI é o ohm-metro. A resistividade também pode ser definida como a razão do campo elétrico e da densidade de corrente. Quanto maior for a resistividade, maior será o campo necessário para produzir uma determinada densidade de corrente. Quanto menor for a resistividade, maior será a densidade de corrente produzida por um determinado campo elétrico. Como listado na Tabela 1, bons condutores apresentam alta condutividade e baixa resistividade, enquanto bons isolantes apresentam baixa condutividade e alta resistividade.

Tabela:1 Lista de valores de resistividade e condutividade para vários materiais.

<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;">Materiais</td>
			<td style="color: black; border: 1px solid black; text-align: center;">Condutividade, σ 
			( Ω · m)−1</td>
			<td style="color: black; border: 1px solid black; text-align: center;">Resistividade, ρ 
			( Ω · m)</td>
			<td style="color: black; border: 1px solid black; text-align: center;">Temperatura 
			Coeficiente, α (°C)−1</td>
		</tr>
		<tr>
			<td style="color: black; border: 1px solid black; text-align: center;">Prata</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;">Cobre</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;">Ouro</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;">Alumínio</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;">Tungstênio</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;">Carbono (puro)</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;">Silício</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;">Âmbar</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;">Vidro</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;">Lucita</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>

Resistividade

Quando uma tensão é aplicada a um condutor, um campo elétrico é gerado e as cargas no condutor sentem a força devido ao campo elétrico. O...

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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

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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...

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Resistivity in Conductors and Insulators

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