Capacitors are electronic components that are made up of two metal plates separated by a dielectric or insulated material. All forms of capacitors are basically use to store current or electricity in form of static electric charges.
Capacitors are also known as condensers, the first types are called lyden jars.
When capacitors are connected to a direct current source, it doesn't allow current to flow because of the insulating or dielectric material between it metal plates. However, if alternating current is passed through it, flows across it without any obstruction.
How do capacitors store electricity?
Capacitor connected to a power supply.
Capacitors stores electricity with the help of two metals seperated by an insulator (dielectric).
When connected to DC, potential electrostatic charges builds up at the plates, the plate connected to the - polarity possess only negative charges while the positive consists only positive charges.
A capacitor is fully charged when the plates are fully occupied with charges and it have the same voltage as the power source it is connected to. When a fully charged capacitor is connected to an LED, it glows for some seconds and die down, the amount of time it takes to glow before dying depends on it capacitance (measured in farad).
For example a 1000uf capacitor will take long time to continue supplying current to an LED than an 100uf capacitor.
Capacitance of a capacitor.
Capacitance is the amount of charges a capacitor can store or amount or time taken for it to supply current to a load when fully charged.
Capacitance is measured in farad.
Capacitors capacitance can't be written in farad because it will look to lengthy for example 0.00000000001uF, instead they are shorted with prefixes, the above lengthy capacitance is shorted to 1PF.
Here are the most common prefixes and their values.
1000000...........M
1000...................k
0.001..................m
0.000001...........u
Factors affecting capacitance.
The capacitance of a capacitor depends on the following factors;
1.Size of the metal plates.
the bigger the size of a capacitor's plates the more the capacitance, because the plates can hold much charges than a smaller one.
2.Distance between the plates.
The smaller the distance between the plates the larger its capacitance. Large distance between the plates results in low capacitance.
Nature of the dielectric material between the plates.
The nature of the dielectric material seperating the plates depends on the capacitance of the capacitor. Dielectric materials with great insulating ability tends to increase capacitance.
Capacitors voltage rating(working voltage).
All capacitors are usually marked with their voltage rating. Voltage rating means the maximum voltage a capacitor can work on.
A capacitor with a voltage rating of 25v can only be used in circuits having 24v or below.
Most usually if a circuit runs on 25v a capacitor of 50v rating must be used to avoid swelling and explosion.

When high voltage is applied to a capacitor with low working voltage it swells up followed by explosi
on.
Applications of capacitors.
Capacitors has many applications in circuits such as;
1.Regulation of fluctuating DC. 2.Purifying rectified DC from AC
3.Use for reducing sparks in RF circuits.
4.It's ability to block DC from flowing finds it applications in smoothing output voltages of power supplies and removal of unwanted signals during transmission that would otherwise cause damages or false triggering of semiconductors and digital components.
It is use with inductors to tune to different frequencies in a radio receiver circuit.