The capacitor is an essential component in many electronic circuits, functioning as a reservoir
temporary electricity supply. A capacitor's ability to store charge is measured in
Basically, the capacitor consists of two metal plates parallel to each other.
One of the plates assumes positive charge and the other negative charge. Usually who provides
these charges to the capacitor is a source of voltage or current. This distribution of
charges generates a uniform electric field between the plates, oriented of the plate with charge
positive for the negatively charged plate. Is due to this
In the
There is also a constant of proportionality,
called
The capacitance of a capacitor with a given geometry and dielectric
between its plates can be calculated through the
Where the variables are:
Thus, for each material used as dielectric we have a constant with numerical values
which will imply different capacitance values. It should be noted that for
the
Material of Dieletric | Perm. Relative (ε_{r} ou K) |
Vaccum | 1.00000 |
Air | 1.00059 |
Water 20°C | 80.40 |
Water 25°C | 78.50 |
Ethanol | 25 |
Germanium | 16 |
Silicon | 12 |
Aluminium | 8.10 a 9.50 |
Soapstone (M_{g}O - S_{i}O_{2}) | 5.50 a 7.20 |
Mica | 5,400 a 8,700 |
Oil | 4.6000 |
Paper | 4.00 a 6.00 |
Waxer Paper | 2.50 |
Plastic | 3.00 |
Polystyrene | 2.50 |
Porcelain | 6.00 |
Pyrex | 5.10 |
Titanates | 50 a 10,000 |
In practice, there are several types of capacitors that depend on which material is
used as
From the year 2 000, another type of capacitor called
As with the resistors, we have three types of capacitor associations that we can find
in electrical circuits. The
3.1. Series Association
What characterizes an association
In the
3.2. Parallel Association
What characterizes a
In the
In this case, we will have
that the value of total capacitance of the association will be given by the sum of all
capacitances that are part of the circuit. Then, to calculate the total capacitance of a parallel association,
for any number of capacitors, we use the
3.3. Mixed Association
In the
To calculate the total capacitance of a mixed association, we must calculate the capacitance capacitors that are associated in parallel and calculate the capacitance in series associations until you reach the final result. With this calculated value, we can calculate the total charge supplied by the voltage source.
To calculate the partial charge of each capacitor in the circuit, we must go back capacitor to capacitor, not forgetting that capacitors that are in a series circuit will have the same charge regardless of the value of their capacitance. Therefore, the value of the voltage between the each capacitor in a series circuit will depend only on its capacitance.
Since the capacitor generates an electric field between the plates, then it is able to
store energy. Remember that the unit of measure of energy is
We must always keep in mind that a capacitor maintains a direct relation between
In this item we will study the behavior of a capacitor in relation to
Below are two fundamental properties of a capacitor.
Based on the above properties the capacitor assumes characteristics
when subjected to voltage variations at its terminals. Normally,
a resistor in series with the capacitor is used to limit the current
in the capacitor. Thus, when the capacitor is subjected,
In this circuit we have a key
At the time of closing the
At the instant immediately after
Knowing the
We see in the
When the capacitor reaches its maximum electric charge, we say that the circuit has reached
the state of
Now, stay tuned for the fact that as the voltage in the
capacitor
In the
Realize that when the voltage
on the capacitor
Notice that this graph also represents the voltage drop on the
This was a brief approach on the behavior of a capacitor when this is in a circuit that uses DC only. We will soon address with this problem, using the solution of differential equations, as well as to demonstrate where the above equations came from. If you want to access this chapter click here!