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The capacitor is a electrical/electronic device made of two metal plates separated by an insulator or dielectric. A dielectric or an insulator is a material that prevents the flow of the current from one plate to the other.
The capacitor symbol is:
The capacitor stores energy in the form of an electric field (it is clear when the capacitor works with direct current) and the capacitance is the amount of electric charges that it is capable to store
The capacitance depends on the physical characteristics of the capacitor.
- If the area of the plates that are face to face is large the capacitance increases.
- If the gap between plates increases, the capacitance decreases.
- The type of dielectric material between the plates also affects the capacitance.
- If you increase the applied voltage, the stored charge increases.
Dielectric
The dielectric is used to increase the capacitance of the capacitor. Different materials are used as dielectric. These materials have different degrees of permittivity. (different capacities for the establishment of an electric field)
| Material |
Relative Permittivity (Er) |
| Vaccum |
1 |
| Air |
1.0059 |
| Polyethylene |
2.5 |
| Porcelain |
5 ... 6 |
| Mica |
7 |
| Tantalum pentoxide |
26 |
| Ceramic |
10 to 50000 |
The greater the permittivity, the greater the capacitance of the capacitor
The capacitance of a capacitor is given by: C = Er x A/d
where:
- C = capacitance
- Er = permittivity
- A = area between plates
- D = separation between the plates
The unit of measurement is the farad. There are submultiples such as: miliFarad (mF), microFarad (UF), nanoFarad (nF) and picoFarad (pF)
The main electrical features of the capacitor are its capacitance and the maximum voltage between the plates (maximum voltage that can withstand the capacitor without damage).
Never connect a capacitor to a higher voltage
that it can withstand since it can exploit.
Related Links
- Inductor
- Conductors
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