This presentation introduces capacitors and their mechanism. It is presented by the CRYOGENICS group which includes 5 members. The document defines a capacitor as a passive two-terminal electrical component that stores energy in its electric field. It explains how capacitors work by storing positive and negative charges on opposing plates when connected to a battery. The document also covers the basic construction of capacitors, types of capacitors including mica, ceramic and plastic film, and variable capacitors.

1. Welcome To Our Presentation

2. Mechanism of Capacitor
Course Teacher:Md. Rasel Hosen

3. GROUP NAME:
CRYOGENICS
Our group members..
1.Foysal Ahmed ID:171-15-9041
2.Isthtiak Ahmed ID:171-15-9062
3.Zahidul Islam ID:171-15-8786
4.Shoeb Shawon ID:171-15-8614
5.Mahather Mohammad ID:171-15-9106

4. Capacitors
 A capacitor is a passive two-terminal electrical
component used to store energy in its electric field.
 When a capacitor is attached across a battery. An
electric field develops across the dielectric,
causing positive charge +Q to effect on one plate
and negative charge –Q to collect on the other
plate.
 The unit of capacitance is Farads (F)

5. Capacitors
 Basic capacitor construction
Dielectric
material
Plate 1
Plate 2
The dielectric
material is an
insulator therefore
no current flows
through the
capacitor

6. Capacitors
Storing a charge between
the plates
 Electrons on the left
plate are attracted
toward the positive
terminal of the voltage
source
 This leaves an excess of
positively charged holes
 The electrons are
pushed toward the right
plate
 Excess electrons leave a
negative charge
+ -
+
_
+ _

7. Capacitors
Types of capacitors
 The dielectric material
determines the type of
capacitor
 Common types of
capacitors are:
 Mica
 Ceramic
 Plastic film

8. Capacitors
 Some capacitors are
polarised, they can
only be connected
one way around
 Electrolytic
capacitors are
polarised

9. Capacitors
 Variable capacitors are
used in communication
equipment, radios,
televisions and VCRs
 They can be adjusted by
consumers by tuning
controls
 Trimmers are internal
adjusted capacitors
that a consumer cannot
adjust

10. Capacitors
 These variable
capacitors would be
difficult to squeeze
into your mobile
phone and iPod
 Current technology
uses semi-conductor
variable capacitors
called varactors
(varicaps)

11. Capacitors
 The capacitance in a
varactor is created
when a purpose diode is
reversed biased
 Adjusting the reverse
bias alters the
capacitance value
 A simple radio receiver
using varactor