Charging a parallel plate capacitor.

In summary, the capacitance of a parallel-plate capacitor can be calculated using the formula C = εA/d, where C is the capacitance in Farads, ε is the permittivity of the dielectric, A is the area of the plates in square meters, and d is the separation of the plates in meters. If the dielectric is air, the formula can be simplified to C (in pF) = 0.0885 * Area ( in square cm) / separation distance (in cm). So, for example, if the plates were 10 cm * 10 cm with a separation distance of 0.5 cm, the capacitance would be 17.5 pF. The voltage on the
  • #1
tntenigma
1
0
I'm building a parallel-plate capacitor for a capacitance sensing circuit. If I let the capacitor fully charge, and then pulled the plates apart by 5 cm, how would that change the capacitance? Is there a formula to figure that out?
 
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  • #2
welcome to pf!

hi tntenigma! welcome to pf! :smile:

for a capacitor of area A and separation d …

C = Q/V

V = -Ed

E = D/ε

D = -Q/A

so C = εA/d :wink:
 
  • #3
You can calculate the capacitance as follows:

C = εA/d

Where
C= capacitance in Farads
ε = 8.854 * 10 ^-12 Farads per meter
A = area of plates in square meters
d = separation of plates in meters

The capacitance does not depend on the voltage on the capacitor, only on the dimensions and permittivity of the dielectric.

If the dielectric is air, this formula can be simplified as follows:
C (in pF) = 0.0885 * Area ( in square cm) / separation distance (in cm)

So, if the plates were 10 cm * 10 cm that is 100 sq cm
If these were 0.5 cm apart,
C = 0.0885 * 100 / 0.5 = 17.5 pF
 

What is a parallel plate capacitor?

A parallel plate capacitor is a type of electrical component that is made up of two parallel conductive plates separated by a dielectric material. It is used to store electrical charge and is commonly found in electronic devices.

How does a parallel plate capacitor work?

A parallel plate capacitor works by creating an electric field between the two conductive plates. When a voltage is applied, one plate becomes positively charged and the other becomes negatively charged, creating an electric potential difference between the plates. The dielectric material between the plates helps to maintain this charge separation.

What factors affect the capacitance of a parallel plate capacitor?

The capacitance of a parallel plate capacitor is affected by the area of the plates, the distance between the plates, and the type of dielectric material used. Generally, a larger plate area and smaller distance between plates will result in a higher capacitance, while a higher dielectric constant of the material will also increase capacitance.

How do you charge a parallel plate capacitor?

To charge a parallel plate capacitor, you can connect it to a battery or power source with a switch in between. When the switch is closed, the capacitor will begin to charge as the electric field is created between the plates. The time it takes to charge the capacitor depends on its capacitance and the voltage of the power source.

How do you calculate the capacitance of a parallel plate capacitor?

The capacitance of a parallel plate capacitor can be calculated using the formula C = εA/d, where C is the capacitance in farads, ε is the permittivity of the dielectric material, A is the area of the plates, and d is the distance between the plates. The unit of capacitance, farads, is equivalent to coulombs per volt.

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