1. The document summarizes the key aspects of capacitors including their history, construction, symbols, circuit configurations, capacitance, and dielectrics.
2. A capacitor consists of two parallel metal plates separated by a vacuum, air, or other insulator. Charges of equal magnitude but opposite polarity develop on the plates when a voltage is applied.
3. Capacitors can be connected in series or parallel in electric circuits. In series, the total capacitance is less than the smallest individual capacitance. In parallel, the total capacitance is the sum of the individual capacitances.
3. Introduction:
In 1745, the Dutch physicist Pieter Van
Musschenbroek of Leiden(Leyden) invented a similar
capacitor, which was named the Leyden Jar after
the University of Leiden where he worked.
Daniel Gralath was the
first to combine several jars in
parallel.
Benjamin Franklin
came to conclusion that the
charge was stored on the
glass, not in water. He also
adopted the term
“Battery”.
7. Working:
Let the plates of such a capacitor are connected to a
battery of voltages V. It produces a potential difference
of V volts between two plates. The charge +Q is
deposited on the plate connected to positive terminal
and charge –Q on the plate connected to negative
terminal of the battery.
Mathematical Expression:
Q ∝ V
Q = CV
Q is the Charge, V is the voltage and C is capacitance.
8. Capacitor in circuit :
There are 2 Ways in which an electric circuit
can be arranged by using Capacitor:
1. Series
2. Parallel
9. Series Circuit:
The inverse equivalent capacitance of two or more
capacitor in series combination is equal to the sum of
the inverse of the individual capacitance.
Voltages are different.
Charges are same.
V
-+
-+
-+
C1 C2
10. CT = C eq
Mathematical Expression:
Where C1,C2 and C3 are
capacitances of three capacitors
11. Parallel Circuit:
The equivalent capacitance of two or more capacitor in
series combination is equal to the sum of the
individual capacitance.
Charges are different.
Voltages are same.
V
-
++
C1 C2-
+
14. Capacitance:
Definition:
“It is the measure of how much charge must be put
on plates to produce certain potential difference.”
OR
“The amount of charge on either plate required to
raise the potential difference between two plates.”
Mathematical Expression:
C = Q / V
It depends upon the geometry of the plates and
the medium between them.
15. Unit and Examples:
The System International Unit of Capacitance
is Farad denoted by F.
F = C V
-1
• Capacitor are used in every electronic machine.
For example Telephone, Mobile, Finger
print machine even every Electronic device has
Capacitor in its circuit.
16. Capacitance of parallel plate
Capacitor:
When vacuum or air is between two parallel
capacitor: +Q-Q
V
- +
Mathematical Expression:
C=દ0 A / d
The Capacitance of a capacitor depends upon the area ‘A’ of
plates and the separation ‘d’ between the plates and medium
between them.
17. Capacitance of parallel plate
Capacitor:
When di-electric is used between two parallel
capacitor:
Di-electric:
The insulator placed between two plates is called
“Di-electric”.
• If a di-electric, of relative permittivity દr is placed
between the plates, the capacitance of capacitor is increased
by the factor દr .
Mathematical Expression:
C med = દ0 દr A / d
18. +Q-Q
V
- +
Di-electric
•When a di-electric
material is placed between
the, reading of potential
difference between the
plates drops.
Relative di-electric:
“The ratio of the capacitance of a parallel plate
capacitor with an insulating medium between the
plates to its capacitance with vacuum as medium
between them.”
Mathematical expression:
દr = Cmed / Cvac
