UNIT 5 : CAPACITORS AND CAPACITANCE

UNIT 5 :
CAPACITORS AND CAPACITANCE

Permittivity is a capacitance or ability to store energy of a capacitor.A force was also generated, known as electric force and the symbol. It depends on the dielectric substance, and the symbol is ɸ.

CAPACITOR AND CAPACITANCE

CAPACITOR EQUIVALENTS CIRCUIT

CIRCUIT WITH CAPACITIVE LOAD

PROCESS CHARGING AND DISCHARGING IN CAPACITOR

TYPES OF CAPACITORS

CAPACITOR CONSTRUCTION

CHARGING PROCESS IN CAPACITOR

DISCHARGING PROCESS IN CAPACITOR

ENERGY STORED IN A CAPACITOR

CAPACITOR CONNECTED IN PARALLEL

CAPACITOR CONNECTED IN SERIES - PARALLEL

ELEMENTS RELATED TO CAPACITANCE

FACTOR THAT EFFECTING CAPACITANCE

ASSOCIATED QUANTITIES

1) Microfarad (μF) : 1μF = 1/1,000,000F = 10^(-6)F
2) Nanofarad (nF) : 1nF = 1/1,000,000,000F = 10^(-9)F
3) Microfarad (pF) : 1pF = 1/1,000,000,000,000 = 10^(-12)F

used to store electrical energy.

The unit of capacitance is Farad. The symbol of capacitance is C.

Capacitance is defined to be the amount of charge Q stored in between the two
plates for a potential difference or voltage V existing across the plates.

FIXED

VARIABLE

UNPOLARISED

POLARIZED

TRIMMER

MICA

CERAMIC

FILM

AIR - GAP

PAPER

ALUMINIUM

TANTALUM

The simplest construction of a capacitor is by using two parallel conducting metal plates separated through a distance by an insulating material, called a the dielectric as summarised below. A capacitor consists of two metal plates separated by a dielectric

The dielectric material allows for charge to accumulate between the capacitor plates.
Air ;actually vacuumͿ has the lowest dielectric value of ɸo = 8.854 x 10^(-12) Farads/meter. All other
materials have higher dielectric values, since they are higher in density and can therefore
accumulate more charge.

CIRCUIT CONNECTED IN SERIES

a. Capacitance between two plates proportional to the surface area

b. Capacitance between two plates inversely proportional to the thickness of dielectric

c. Increasing the dielectric constant of the material between the plates

During charging process through capacitor, it will get energy. Energy is kept in
static form.The voltage in capacitor will increase from 0 volt to E volt.

W = 1 / 2 ( C(E^2)) Joule

When capacitor fully charge and then switch being transformed to ͚b͕͛ discharge process for capacitor will happen. The time taken to recharge and fully discharge is 5τ=CxR.

In initial state, a capacitor is uncharged( Vc = 0V). When a capacitor start
charged, maximum current will be flowing (i = I(max).. The current would be decreased by
exponent, while voltage will be rising by exponent also. This state will continue until fullstate (steady) achieved. In this full state, current had decreased to zero value, while voltage increased until maximum value. The capacitor is s said in fully charge.

Time constant,τ= CR
The times taken for voltage achieve value of 0.632Vmax and current achieve value of
0.371 I(max)
Initial current,I(max) = V/R

ELECTRIC FIELD

LINE OF ELECTRIC FORCE

ELECTRIC FLUX

ELECTRIC FLUX DENSITY (D)

ELECTRIC FIELD STRENGTH

DIELECTRIC

ABSOLUTE PERMITTIVITY (ɸ)

Area that surrounds the electric charge or charges system where the
increasing and decreasing of electric force exists.

A line of electric force is known as line or curve that pointed out from
positive charge (+) to negative charge (-) in a magnetic field.

When two metal plates are charged and separated in a certain distance, a
potential difference will exists between the plates.

ɸ = D / E

Insulator that is used between the two plates of a capacitance is known as
dielectric.

Electric field exists in the dielectric and the flux density depends on the types
of insulator used.

Known as amount of electric force line pointed out from positive charge (+)
to negative charge (-) in a magnetic field. Flux symbol is Ψ(phi).

A force was also generated, known as electric force and the symbol is E. The magnetic strength depends on the potential difference and distance between plates.

E = V / d
V= potential difference, d= thickness of dielectric

Electric flux density is a measurement of electric flux that pass through a
unit of plate͛s area with a coincide angle͕ that is an area of 1 meter^2

The ratio between the charge of the capacitor and capacitor plates.The symbol used is D.
D = Q/A
Q= charge(Coulomb),A = surface area of capacitor

UNIT 6:
INDUCTOR AND INDUCTANCE

Inductor and inductance

Inductance equivalents circuit for series and parallel connection

Rise and decay of current goes through an inductor in the dc circuit

Circuit with inductive load

Construction of inductor

Associated quantities

Types of inductor

1) Inductor, also called a choke, is another passive type electrical component designed to take advantage of this relationship by producing a much stronger magnetic field than one that would be produced by a simple coil.
2) Symbol of inductance is L.
3)Unit of inductance is Henry. 4)Inductance ʹ the property of an electric circuit by which an electromotive force is
induced in it as the result of changing magnetic flux. 5)Electromagnet ʹ temporary magnet production due to flow of electric current.
6)Electromagnetic induction - production process electric form magnet.

An inductor is usually constructed as a coil of conducting material, typically
copper wire, wrapped around a core either of air or ferrous material.
Core materials with higher permeability than air confine the magnetic field
closely to the inductor, thereby increasing the inductance.
constructed as enamel coated wire wrapped around a ferrite with wire
exposed on the outside, while some enclose the wire completely in ferrite and are called
͚shielded͛͘

Inductors connected in series

Inductors connected in parallel

Inductors connected in series-parallel

Time constant

Energy stored in an inductor

Rise and decay of current

An inductor possesses an ability to store energy.
E = (1/2)(L(I^2))

Electromagnetic induction

Faraday's Law

The factors that influence inductance

The mathematical of self-inductance

Self-inductance and the induced e.m.f

Mathematical relationship between the induced e.m.f and the network

The cross-sectional area of the coil of wire (A) ʹ the greater the cross-sectional area
the higher the inductance

The presence of magnetic core - when the coil is wound on an iron core, the same
current sets up a more concentrated magnetic field and the inductance is increased

The number of turns of wire (N) ʹ more turns the higher the inductance

The way turns are arranged ʹ a short tick coil of wire has a higher inductance than
the along thin one.

When a conductor is moved across a magnetic field so as to cut through the lines of
force (or flux, an electromotive force (e.m.f) is produced in the conductor.
If the conductor forms part of a closed circuit then the e.m.f produced causes an electric current to flow round the circuit.
Hence an e.m.f is induced in the conductor as a result of its movement across the
magnetic field͘ This effect is known as electromagnetic induction͛͘

An induced e.m.f is setup whenever the magnetic field linking that circuit
changes
The magnitude of the induced e.m.f in any circuit is proportional to the rate of
change of the magnetic flux linking the circuit.

Faraday noted that the e.m.f induced in a loop is proportional to the rate of change of
magnetic flux through it:

Inductance is the name given to the property of a circuit whereby there is an e.m.f
induced into the circuit by change of flux linkages produced by a current change.
When the e.m.f is induced in the same circuit as that in which the current is changing,
the property is called self-inductance, L.

Time constant at rise of current

Time constant at decay of current

1) When switch in 'a' position͕ inductor connected to DC supply.The current had not achieved maximum value immediately.The current are going to reach maximum value in a period of time that certain caused by production e.m.f induced by inductor which always against the supply voltage. So, current of the circuit is rise delayed.
2) When switch is being transformed to position ͚'b' inductor circuit had short
circuit (no supply voltage).The current is not decrease continue to zero but take a time
that certain from maximum value until zero value.