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what is capacitor,Formula,Charge,Discharge a capacitor


A capacitor, also called capacitor is an electrical component that stores electrical charge, to release later. Also called a capacitor. In the next picture we see several different types.


Remember that electric charge is the amount of electricity. If you are not sure what the load or want to know more about cargo and other quantities we recommend the following link: Electrical Quantities.

Consider the operation of capacitors and capacitor types in the world.

    How do you store charges the capacitor?

To store electric charge, using two conductive plates or shaped surfaces separated by a dielectric material (insulating) sheet. These plates are electrically charged that when we connect to a battery or to a voltage source. Plates were loaded with the same amount of charge (q) but with different signs (+ and the other one -). Once we have loaded between two plates d.d.p or tension, and be prepared to drop this charge when we connect to a receiver output.


The dielectric material separating the plates or sheets usually air, tantalum, paper, aluminum, ceramics and certain plastics, dependent capacitor. A dielectric material is used to isolate electrically each components, so must be good insulators. In the case of separating the two sheets capacitor electrically charged.

The amount of stored electric charge is measured in Farads. This unit is very large, so is often used MFD 10 to least 6 farads. 1 uF = 06.10 F. lower unit PF is also used, which are 10 raised at least 12 farads. 1 pF = 10-12 F.

This amount of charge it can store a capacitor is called capacitance and is expressed by the following formula:

C = q / V

q = the charge of one of the two plates. It is measured in coulombs.

V = is the tension or d.d.p between the two ends or plates or what is the same the capacitor voltage. It is measured in volts.

According to the formula a capacitor with a charge of 1 Coulomb with a voltage of 1 volt, will have a capacity of 1 Farad. As we said before this capacitor would be huge, because 1 Farad is a very large capacity unit (occupy an area of approximately 1.011m2 which in practice is impossible).

We could clear the voltage of the capacitor in the above formula and would:

V = q / C

   Loading and discharge of a capacitor:

A capacitor is not discharged instantaneously, the same thing happens if we want to spend on a car of 100 km / h to 120 km / h, could not pass directly, but there is a transitional period. The same goes for cargo, is not instantaneous. As discussed below, this makes capacitors can be used as timers.

Let’s see how loads and unloads a starting from a very simple circuit capacitor, in which we have only an output resistor R2 and a switch, stop charging or discharging the capacitor, depending on their position. R1, as we shall see is to control the charging time and is called load resistance.

Load Condenser


By putting the switch in position above circuit, the capacitor is in series with R2 and will be charging.

The charging time depends on the capacitance and resistance we have put in series with it. The resistance does is prevent the passage of the current, so the higher this, the greater the charge time, electrons flowing through the circuit will slow to the condenser because of the resistance.

Look at the graph of time depending on the voltage of the capacitor, the capacitor is charging to reach full capacity after 5 x R1 x C seconds.

What if we do not put the load resistor R1 ?. According to the formula when R1 = 0, the capacitor is charged instantaneously, but not so that the capacitor itself has a small resistance, for calculations is considered negligible compared to R1.

Anyway it is not advisable to charge a capacitor directly without load resistor as the load current may be very high and damage the condenser. Remember I = V / R (Ohm’s law). If R is very small, I will be very large. If the capacitor current would be I = V / Icondensador, as R capacitor is very small capacitor would be charged with a very large I. This could make the circuit conductors and the capacitor itself does not support it and burn.

 What happens once the capacitor is fully charged ?. Once the capacitor has been charged, no longer you need battery charge and therefore behave as an open switch. between the two ends of the capacitor would have a d.d.p, the condenser, but not have current flow through it, that is the ‘I” by the capacitor will be 0 amps, but will voltage.

In the above after a time circuit capacitor is charged and the battery will not supply more current to the capacitor, the capacitor is charged and act as an open switch. Eye at the time to change the position of the switch, the capacitor will discharge on R2 and if that current flows through it. We see this below.

    Capacitor discharge:

As you see in the diagram, we have changed the switch position and now the charge on the capacitor is discharged on the output resistor R2.

As before, this discharge will not be instantaneous, will depend on the output R2 and the capacitor. The formula for charging and discharging the capacitor is the same. The higher R2 longer download.

If in addition to the R2 we put another receptor, such as an LED or a lamp, we could control the time it is lit, it will be the duration of the discharge through R2 and the LED or lamp. Also, if the R2 out a potentiometer (variable resistor), we could vary the discharge time of changing the value of the potentiometer resistance. ‘We have built a timer !!!. Here’s the circuit:


EYE same way is not recommended without charge a capacitor R1, neither is download it directly without R2, we would be causing a short circuit, with a very large discharge and therefore I also could burn the condenser.

    The capacitor as filter:

Look at the following circuit:


We have a capacitor in parallel with a resistor, fed by an alternating current (look at the shape of the waves in the drawing). Let us explain what happens in this circuit.

At the initial instant the capacitor is discharged and the supply voltage loads. After a time capacitor is fully charged. What happens now? Now the capacitor begins to discharge by RL, but almost just start downloading, the AC generator detects this and starts charging the capacitor again. The capacitor never discharges completely.

Tension in Rl or output, being in parallel with the capacitor, is the same as having the capacitor, so the wave of the output voltage will be that of the graph to the right, a ground wave, so that only you have the crest of the wave. This is used, for example, for a power supply.



Types of Capacitors

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