23.8
도체가 외부 전기장에 배치되면 도체의 자유 전하가 재분배되어 매우 빠르게 정전기 평형에 도달합니다. 결과적인 전하 분포와 전기장은 가우스 법칙의 도움으로 조사할 수 있는 많은 흥미로운 특성을 가지고 있습니다.
양전하 근처에 금속 조각이 놓여 있다고 가정해 보겠습니다.…
외부 전기장에 배치된 도체를 고려하십시오. 도체에서는 전자만 자유롭게 움직일 수 있습니다.
자유 전자는 외부 전기장 반대편으로 이동하여 표면의 한쪽 끝에 축적됩니다.
결과적으로, 표면의 다른 쪽 끝은 더 적은 수의 전자를 가지므로 순 반대 표면 전하를 얻어 도체를 분극화합니다.
표면 전하의 축적으로 인해 내부 전기장이 외부 자기장 반대편에서 발생합니다.
전하가 계속 이동함에 따라 내부 자기장 크기가 외부 자기장과 같아질 때까지 증가합니다.
도체는 이제 정전기 평형으로 알려진 정상 상태에 도달하고 전하는 더 이상 움직이지 않습니다.
이 상태에서는 도체 내부의 모든 지점에서 외부 필드와 내부 필드의 합인 네트 필드가 사라집니다.
가우스의 법칙에서 전기장이 0이라는 것은 도체 내부에 포함된 순 전하가 없음을 의미합니다.
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Q1: Why is the electric field zero inside a conductor at electrostatic equilibrium?
At electrostatic equilibrium, free electrons in the conductor migrate until they create an induced electric field that exactly opposes the external field. The net field inside becomes zero because the external and internal fields cancel completely. From Gauss's law, a zero electric field means no net charge is enclosed within the conductor's volume.
Q2: What happens to free electrons when a conductor is placed in an external electric field?
Free electrons migrate opposite to the external electric field direction, accumulating at one surface of the conductor. This creates a region with excess electrons and a region with fewer electrons, causing the conductor to polarize. The electron movement continues until the induced electric field balances the external field, establishing electrostatic equilibrium.
Q3: How does conductor polarization relate to surface charge distribution?
When a conductor polarizes, electrons accumulate at one end, creating a negatively charged region, while the opposite end becomes positively charged due to electron depletion. These opposite charges at the surface generate an induced electric field inside the conductor. The surface charge distribution is responsible for creating the internal field that eventually cancels the external field.
Q4: What does Gauss's law tell us about charge inside a conductor?
Gauss's law states that the electric flux through a closed surface equals the enclosed charge divided by permittivity. Since the electric field inside a conductor is zero at equilibrium, the flux is zero, meaning no net charge exists inside the conductor. All excess charge resides on the conductor's surface.
Q5: How long does it take for a conductor to reach electrostatic equilibrium?
A conductor reaches electrostatic equilibrium very quickly when placed in an external electric field. Free electrons rapidly redistribute across the conductor until the induced electric field matches the external field magnitude. This rapid charge redistribution establishes the equilibrium state where the net field vanishes and electron motion ceases.
Q6: What is the relationship between the external field and the induced field inside a conductor?
The induced electric field inside a conductor develops opposite to the external field direction as electrons accumulate at the surface. At electrostatic equilibrium, the induced field magnitude equals the external field magnitude, causing their vector sum to be zero. This balance prevents further charge movement and maintains the zero net field condition.
Q7: Does conductor polarization persist after an external charge is removed?
No, conductor polarization is temporary and depends on the presence of external charges. When the external charge is removed, the separated electrons migrate back and neutralize the positive region. The conductor returns to its neutral state, and the induced electric field disappears.