This document discusses the objective and key concepts regarding capacitors. It explains that a capacitor consists of two conductive plates separated by an insulator, and its capacitance increases with larger plate area, smaller separation distance, and higher dielectric constant. The document also summarizes that capacitors can be charged and discharged, with the time of discharge determined by the capacitor's capacitance and the resistor's resistance. Finally, it lists common types of capacitors and their uses in applications like energy storage, power conditioning, and oscillators.

2. OBJECTIVE OF LECTURE
 Principle, construction and how charge is stored in
the capacitor
 Electrical properties of a capacitor
 Several types of capacitors
 Charging and discharging of capacitors
 Capacitive reactance
 Uses

3.  Composed of two conductive plates separated by an
insulator (or dielectric).
 Commonly illustrated as two parallel metal plates
separated by a distance, d.
C = e A/d
where e = er eo
er is the relative dielectric constant
eo is the vacuum permittivity
CAPACITORS

4. Capacitance increases with
increasing surface area of the plates,
decreasing spacing between plates, and
increasing the relative dielectric constant of
the insulator between the two plates.
EFFECT OF DIMENSIONS

5. Charge separation in a parallel-plate capacitor
causes an internal electric field. A dielectric
(orange) reduces the field and increases the
capacitance.
EFFECT OF DIELECTRIC ON
CAPACITANCE

6. o Ceramic capacitor
o Electrolytic capacitor
o Tantalum capacitor
o Silver Mica capacitor
o Polystyrene capacitor
o Metallised polyester film
o Polycarbonate capacitor
o Polypropylene capacitor
o Glass capacitor
o Supercapacitor
TYPES OF CAPACITORS

7. The basic construction of all capacitors is
similar. The construction of capacitor is very
simple. A capacitor is made of two electrically
conductive plates placed close to each other,
but they do not touch each other. These
conductive plates are normally made of
materials such as aluminium, brass, or copper.
CONSTRUCTION

8.  In a simple parallel-plate capacitor, a voltage applied between
two conductive plates creates a uniform electric field between
those plates. The electric field strength in a capacitor is directly
proportional to the voltage applied and inversely proportional to
the distance between the plates.
ELECTRIC FIELD OF CAPACITOR

9. CHARGING AND DISCHARGING OF
CAPACITOR
Vc
When the Vc
becomes equal
to power
supply voltage
V0 the capacitor
is fully charged.
When the
capacitor
discharges across
the resistor R the
voltage Vc
gradually
decreases and
drops to zero.

10. The product of resistance R and the capacitance C is
called the time constant t.
t = R * C
A fully charged capacitor discharges to 63% of its
voltage after one time period. After 5 time periods it
has almost completely discharged all of its voltage.
Hence time taken to discharge = 5*time constant
TIME OF DISCHARGE OF
CAPACITOR

11. Time taken to discharge
the capacitor is,
=R × C
=(3k )×(1000 F)
= 3 sec × 5
= 15 seconds
r
DURATION OF DISCHARGE

12.  Capacitive reactance (XC) is a measure of
a capacitor's opposition to AC. Like resistance it is
measured in ohms, but it’s more complex than
resistance because its value depends on the.
frequency (f) of the electrical signal passing through
the capacitor as well.
CAPACITIVE REACTANCE

13. Capacitors are installed across many circuits & switching
points to absorb voltage fluctuation.
 Energy storage
 Power conditioning
 Coupling and Decoupling
 Motor starters
 Oscillators
 Time dependent circuits
USES OF CAPACITORS