# Electric field between parallel plates

• lys04
lys04
Homework Statement
The electric field outside a conducting plate of charge is given by sigma/epsilon right? Then why not for a capacitor, since that is 2 conducting plates, is the electric field 2sigma/epsilon using superposition principle?
Relevant Equations
E=sigma/epsilon
^^

Here’s a cross -section through (due to space limitations, part of) an infinite conducting plate with a (say) positive charge:
___________________________
___________________________

Here are some questions to consider:
- are both surfaces charged?
- if only one (of the two) surfaces is charged, what determines which one?
- in a static situation, every ‘field line’ starts on a positive charge and ends on a negative charge; where are the negative charges here?

MatinSAR
lys04 said:
Homework Statement: The electric field outside a conducting plate of charge is given by sigma/epsilon right? Then why not for a capacitor, since that is 2 conducting plates, is the electric field 2sigma/epsilon using superposition principle?
Relevant Equations: E=sigma/epsilon
Generally, the two plates of a capacitor are oppositely charged. Right?

So, if one plate has a surface charge density, ##\sigma##, then the other plate has surface charge density, ##-
\sigma##,

Now use superposition to determine the electric field outside the plates as well as between the plates.

MatinSAR
Tom.G said:
The error in post #1 is much more fundamental than any concerns about fringing effects.

MatinSAR, vanhees71, SammyS and 1 other person

## What is the electric field between two parallel plates?

The electric field between two parallel plates is a uniform field created by the potential difference (voltage) applied across the plates. It is calculated as the voltage difference divided by the distance between the plates, E = V/d, where E is the electric field, V is the voltage, and d is the separation distance.

## How do you calculate the electric field strength between parallel plates?

The electric field strength (E) between parallel plates can be calculated using the formula E = V/d, where V is the voltage applied across the plates and d is the distance between them. The result is expressed in volts per meter (V/m).

## What factors affect the electric field between parallel plates?

The electric field between parallel plates is primarily affected by the voltage applied across the plates and the distance between them. Increasing the voltage increases the electric field strength, while increasing the distance between the plates decreases the electric field strength.

## Is the electric field between parallel plates always uniform?

Yes, the electric field between two large, closely spaced, parallel plates is generally considered to be uniform across the region between the plates. This uniformity holds true as long as edge effects, which occur near the edges of the plates, are negligible.

## How does the presence of a dielectric material between parallel plates affect the electric field?

The presence of a dielectric material between parallel plates reduces the electric field strength. This is because the dielectric material increases the capacitance of the plates, allowing them to store more charge for the same applied voltage. The electric field in the presence of a dielectric is given by E = V/(d * κ), where κ is the dielectric constant of the material.

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