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Capacitors
Capacitance is the ability of a circuit to store an electric charge, so a capacitor is used to store electrical energy.
It consists of 2 conductive plates separated by a thin insulating material (dielectric) which can be air, paper or any other suitable material.
The amount of energy that a capacitor can store for a given voltage is called its capacitance and it's measured in Farads. It's determined by 3 factors;
- The area of the plates (greater area = greater capacitance)
- The distance between the plates (closer together = greater capacitance)
- The dielectric constant of the dielectric material (higher value = greater capacitance)
"Dielectric constant" is a measure of its effectiveness when compared with that of a vacuum.
Formula:
Capacitance (c) = the charge (q) / the voltage (v)
A capacitor in a DC circuit
When compared to a DC voltage, the capacitor will store energy in the form of electrical charge. The energy it stores is a measure of the work done to build up the charge on the plates, removing electrons from the positive plate and adding them to the negative one.
As the charge builds up, so does the potential difference between the 2 plates which makes it more difficult to add more charge to the capacitor. When the voltage across the plates is equal to the applied voltage, the capacitor is fully charged and an electric field exists between the plates through the dielectric.
The current flow follows the path from one plate through the supply (battery) to the other plate. The dielectric is an insulating material so no current can flow through it, the current across the plates flows through the wires!
Capacitance is the ability of a circuit to store an electric charge, so a capacitor is used to store electrical energy.
It consists of 2 conductive plates separated by a thin insulating material (dielectric) which can be air, paper or any other suitable material.
The amount of energy that a capacitor can store for a given voltage is called its capacitance and it's measured in Farads. It's determined by 3 factors;
- The area of the plates (greater area = greater capacitance)
- The distance between the plates (closer together = greater capacitance)
- The dielectric constant of the dielectric material (higher value = greater capacitance)
"Dielectric constant" is a measure of its effectiveness when compared with that of a vacuum.
Formula:
Capacitance (c) = the charge (q) / the voltage (v)
A capacitor in a DC circuit
When compared to a DC voltage, the capacitor will store energy in the form of electrical charge. The energy it stores is a measure of the work done to build up the charge on the plates, removing electrons from the positive plate and adding them to the negative one.
As the charge builds up, so does the potential difference between the 2 plates which makes it more difficult to add more charge to the capacitor. When the voltage across the plates is equal to the applied voltage, the capacitor is fully charged and an electric field exists between the plates through the dielectric.
The current flow follows the path from one plate through the supply (battery) to the other plate. The dielectric is an insulating material so no current can flow through it, the current across the plates flows through the wires!
