What is the size of the electic field inside a charged conductor? How can the strength of an electric field be quantified? What is a Van der Graaf generator? How do lightning rods serve to protect buildings from lightning strikes? How does permittivity affect electric field intensity? How does the strength of an object's electric field change with distance? How does electric field affect capacitance? How does electric field relate to voltage? As the closed surface S we can make it as small as we conclude that at any point P inside a conductor there is no excess burden, so this should be placed on the surface of the conductor.
Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. In electrostatics, why the electric field inside a conductor is zero?
Ask Question. Asked 9 years, 7 months ago. Active 6 years, 4 months ago. Viewed k times. I have 2 questions: We know that conductors metallic have free electrons which randomly moves in all directions, so how come we can talk about electrostatics which by definition means stationary charges?
Improve this question. Revo Revo Add a comment. Active Oldest Votes. Improve this answer. What about quantum mechanics? Even very small surface charges are made up of bjillions of electrons, so it's fair to use statistical measures. As for the non-static nature of the transient, well, yes. A conductor placed in an electric field will be polarized.
Figure 2 shows the result of placing a neutral conductor in an originally uniform electric field. The field becomes stronger near the conductor but entirely disappears inside it. Figure 2. This illustration shows a spherical conductor in static equilibrium with an originally uniform electric field. Free charges move within the conductor, polarizing it, until the electric field lines are perpendicular to the surface.
The field lines end on excess negative charge on one section of the surface and begin again on excess positive charge on the opposite side. No electric field exists inside the conductor, since free charges in the conductor would continue moving in response to any field until it was neutralized.
Excess charges placed on a spherical conductor repel and move until they are evenly distributed, as shown in Figure 3. Excess charge is forced to the surface until the field inside the conductor is zero.
Outside the conductor, the field is exactly the same as if the conductor were replaced by a point charge at its center equal to the excess charge. Figure 3. The mutual repulsion of excess positive charges on a spherical conductor distributes them uniformly on its surface. The resulting electric field is perpendicular to the surface and zero inside.
Outside the conductor, the field is identical to that of a point charge at the center equal to the excess charge. The properties of a conductor are consistent with the situations already discussed and can be used to analyze any conductor in electrostatic equilibrium.
This can lead to some interesting new insights, such as described below. How can a very uniform electric field be created? Consider a system of two metal plates with opposite charges on them, as shown in Figure 4. The properties of conductors in electrostatic equilibrium indicate that the electric field between the plates will be uniform in strength and direction.
Except near the edges, the excess charges distribute themselves uniformly, producing field lines that are uniformly spaced hence uniform in strength and perpendicular to the surfaces hence uniform in direction, since the plates are flat. The edge effects are less important when the plates are close together. Figure 4. Two metal plates with equal, but opposite, excess charges. The field between them is uniform in strength and direction except near the edges.
One use of such a field is to produce uniform acceleration of charges between the plates, such as in the electron gun of a TV tube. Figure 5. Earth and the ionosphere a layer of charged particles are both conductors.
Parks b Storm fields. In the presence of storm clouds, the local electric fields can be larger. At very high fields, the insulating properties of the air break down and lightning can occur. What causes the electric field? At around km above the surface of Earth we have a layer of charged particles, called the ionosphere. The ionosphere is responsible for a range of phenomena including the electric field surrounding Earth.
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