7.4.2

Parallel Plate Capacitor

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Parallel Plates

A parallel plate capacitor is made of two charged plates separated by a distance. This type of capacitor creates a uniform field.

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Dielectrics

  • A parallel plate capacitor has a gap between the two plates, this gap can be filled with air or a dielectric.
  • A dielectric is a material which increases the capacitance of a capacitor.
    • The dielectric allows a capacitor to store more charge.
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Capacitance

  • The capacitance of a parallel plate capacitor depends on the distance between the plates, the area of the plates and if there is a dielectric. This relationship can be shown with the following equation:
    • Capacitance = area × permittivity of free space × permittivity of dielectric ÷ distance between the plates.
    • C=Aϵ0ϵr/dC=A{{\epsilon}_0}{{\epsilon}_r}/d
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Polar molecules

  • A molecule is made up of a positive nucleus and a negative electron cloud.
  • In a field, the positive nucleus will move slightly in the direction of the field and the negative cloud will move slightly in the other direction.
    • This creates an imbalance in the charge distribution.
  • If this polarized molecule is then put into a field the cloud will be pulled in one direction and the nucleus pushed in the other.
    • This will cause a rotation.

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1Measurements & Errors

2Particles & Radiation

3Waves

4Mechanics & Materials

5Electricity

6Further Mechanics & Thermal Physics (A2 only)

7Fields & Their Consequences (A2 only)

8Nuclear Physics (A2 only)

9Option: Astrophysics (A2 only)

10Option: Medical Physics (A2 only)

11Option: Engineering Physics (A2 only)

12Option: Turning Points in Physics (A2 only)

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