Doubt in parallel plate capacitor

In summary: But inside the metal plate E still exists since it is in a different direction than the outside field.Hence inside the metal plate the electric field still exists.
  • #1
AdityaDev
527
33
I was going through the capacitor lesson in my textbook. In it its written "...both positive and negative plates will produce electric field in the same direction, hence the electric field adds up...outside the plates, electric field is zero since the field due to negative and positive charges are in opposite direction..."
My doubt : i am confused at the 2nd statement. (i have attached two images)
  • which electric fields are in opposite direction? how does it cancel out?
  • Is this true only if the charge on the capacitor plates are same?
  • Do electric fields extend to infinity?
  • does the electric field outside capacitor for second image become zero?
 

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  • #2
What do you think, and why? Then we can correct the specific misconceptions that you have.
 
  • #3
jtbell said:
What do you think, and why? Then we can correct the specific misconceptions that you have.
this is what I think... let the positive plate be on the left and the negative on right. From gauss law, field inside conductor should be zero. Maybe the positive field from left plate extends to right and the negetive from right plate also passes through plate 1 on ...I have no idea...
 
  • #4
Have you looked at images of the fields around a parallel plate capacitor? The situation between the plates is very distinct from the situation outside and at a distance.
This link shows what happens outside.
 
  • #5
AdityaDev said:
and the negetive from right plate also passes through plate 1

You're on the right track here. Do you know about the principle of superposition? Consider the field produced by each plate by itself, as if the other one were not there at all; then add the two fields together.
 
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  • #6
sophiecentaur said:
Have you looked at images of the fields around a parallel plate capacitor? The situation between the plates is very distinct from the situation outside and at a distance.
This link shows what happens outside.
you are going off topic
 
  • #7
jtbell said:
You're on the right track here. Do you know about the principle of superposition? Consider the field produced by each plate by itself, as if the other one were not there at all; then add the two fields together.
Ok.field of -Q charge from the inner surface of left plate passes through the metal plate. the electric field of +Q charge also passes through its own metal plate. Hence inside the metal plate the electric field cancels out. This also happens outside the plate. Hence there also field cancels out.
 
  • #8
AdityaDev said:
Hence inside the metal plate the electric field cancels out.

No... consider the directions of the two fields. The electric field produced by a positive charge points away from the charge, and the electric field produced by a negative charge points towards the charge.
 
  • #9
jtbell said:
No... consider the directions of the two fields. The electric field produced by a positive charge points away from the charge, and the electric field produced by a negative charge points towards the charge.
That is why it cancels out int outer region. One is in +x and other is in -x. But inside both are in same direction.
 
Last edited by a moderator:
  • #10
O
jtbell said:
No... consider the directions of the two fields. The electric field produced by a positive charge points away from the charge, and the electric field produced by a negative charge points towards the charge.
Oops... Outside the metal plate E cancels out
 

1. What is a parallel plate capacitor?

A parallel plate capacitor is a type of capacitor that consists of two parallel conducting plates separated by a dielectric material. It is used to store electrical charge and is commonly used in electronic circuits.

2. How does a parallel plate capacitor work?

A parallel plate capacitor works by creating an electric field between the two plates. When a voltage is applied, one plate becomes positively charged and the other becomes negatively charged. The dielectric material between the plates stores the electrical energy as an electric field.

3. What factors affect the capacitance of a parallel plate capacitor?

The capacitance of a parallel plate capacitor is affected by the distance between the plates, the surface area of the plates, and the relative permittivity of the dielectric material between the plates. As the distance between the plates decreases and the surface area increases, the capacitance increases. A higher permittivity of the dielectric material also increases the capacitance.

4. How is the capacitance of a parallel plate capacitor calculated?

The capacitance of a parallel plate capacitor can be calculated using the formula C = εA/d, where C is the capacitance, ε is the permittivity of the dielectric material, A is the surface area of the plates, and d is the distance between the plates.

5. What are some applications of parallel plate capacitors?

Some common applications of parallel plate capacitors include power supplies, filters, and timing circuits in electronic devices. They are also used in radio frequency circuits, touch sensors, and energy storage systems.

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