Capacitor is a passive electronic component or device capable of storing charge with a
certain voltage level across two conducting plates or surfaces separated by an insulating
material or dielectric substance. Capacitor is constructed by using two conducting surfaces or plates and an insulating material
that is dielectric like mica, paper, air etc. between these two surfaces
As a capacitor is a passive component, it does not generate energy, but it is able to
store energy from an energy source like a battery or another charged capacitor
When a battery or a DC source is connected across a capacitor, one surface named plate
1 gets positive end of the battery and another surface named plate 2 gets the negative end
of the battery. When switch is on, the full voltage of that battery is applied across that capacitor
At that situation, plate 1 is in positive potency with respect to the plate 2
Current from the battery tries to flow through this capacitor from its positive plate or
plate 1 to negative plate or plate 2 but cannot flow at max value due to separation
of these plates with an insulating material. Rather, a very small current will flow through this insulating material or dielectric from
positive to negative plate depending upon the value of strength of this dielectric
An electric field will form inside the capacitor dielectric from positive to negative plate
As time goes on, positive plate or plate 1 will accumulate positive charge from the
battery and negative plate or plate 2 will accumulate negative charge from the negative
end of the battery. After a certain time, the capacitor holds maximum amount of charge as per its capacitance
with respect to this voltage. This time span is called charging time of this capacitor
Now, after removing this battery from this capacitor, these two plates will hold positive
and negative charges with respect to a certain voltage level for long time
Thus, this capacitor acts as energy source. If two ends or plate 1 and plate 2 get shorted through a load, a current will flow through
this load from plate 1 to plate 2 up to all charges get vanished from both plates
This time span is known as discharging time of the capacitor. Suppose a capacitor is connected across a battery through a switch
When switch is on i.e. t is equal to zero plus, a certain value of current will flow
through this capacitor. After a certain time i.e. charging time, capacitor never allows current to flow through it further
It is because of maximum number of charges are accumulated on both surfaces and capacitor
acts as a battery which has positive end connected to the positive end of the battery
and negative end connected to the negative end of the battery with same potency
Due to zero potential difference between battery and capacitor, no current will flow through it
So, it can be said that initially a capacitor is short-circuited and finally open-circuited
when it gets connected across a battery. Suppose a capacitor is connected across an AC source
Consider at a certain moment of positive half of this alternating voltage, plate 1 gets
positive polarity and plate 2 negative polarity. Just at that moment, plate 1 accumulates positive charges and plate 2 accumulates negative charges
But at the negative half of this applied AC voltage, plate 1 gets negative charges and
plate 2 positive charges and so on. There is no flow of electrons between these two plates as they change their polarity with
the change of source polarity. The capacitor plates get charged and discharged alternatively by the AC