What is a Capacitor?

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Capacitors are passive components, similar to a resistor. Charges are usually

stored in the form of an "electrical field" in a capacitor. There are different types of
capacitors such as ceramic capacitors, paper capacitors, etc.

 Many electrical and electronic circuits rely heavily on these.

 A capacitor is made up of two parallel metal plates that are not connected to
one another.
 The capacitor's two plates are separated by a non-conducting medium
(insulating medium), which is called a dielectric.

Capacitors

Capacitance

The capacitance is the ratio of electric charge (Q) to the voltage (V) and the
mathematical expansion is following.

C = Q/V

Where,

 Q is the electric charge in coulombs

 C is the capacitance in farad
 V is the voltage between the plates in volts

Different Types of Capacitors

The different types of capacitors are following.

1. Electrolytic Capacitor
2. Mica Capacitor
3. Paper Capacitor
 4. Film Capacitor
5. Non-Polarized Capacitor
6. Ceramic Capacitor

Electrolytic Capacitor

Generally, the electrolyte capacitors are used when the large capacitor values are
required. The thin metal film layer is used for one electrode and for the second
electrode (cathode) a semi-liquid electrolyte solution which is in jelly or paste is used.
The dielectric plate is a thin layer of oxide, it is developed electrochemically in
production with the thickness of the film and it is less than the ten microns.

Electrolytic Capacitor

This insulating layer is very thin, it is possible to make capacitors with a large value
of capacitance for a physical size, which is in small and the distance between the
two plates is very small. The types of capacitors in the majority of electrolytic are
polarized, which is DC voltage is applied to the capacitor terminal and they must be
correct polarity.

If the positive to the positive terminal and the negative to the negative terminal as an
incorrect polarization will break the insulating oxide layer and there will be permanent
damage. All the polarized electrolytic capacitors have polarity clearly with the
negative sign to show the negative terminal and the polarity should be followed.

The uses of electrolytic capacitors are generally in the DC power supply circuit
because they are large in capacitance and small in reducing the ripple voltage. The
applications of this electrolytic capacitors are coupling and decoupling. The
disadvantage of the electrolytic capacitors is their relatively low voltage rating
because of the polarization of electrolytic capacitor.

Mica Capacitor

This capacitor is a group of natural minerals and the silver mica capacitors use the
dielectric. There are two types of mica capacitors which are clamped capacitors &
silver mica capacitor. Clamped mica capacitors are considered as an obsolete
because of their inferior characteristic. The silver mica capacitors are prepared by
sandwiching mica sheet coated with metal on both sides and this assembly is then
encased in epoxy to protect the environment. The mica capacitors are used in the
design calls for stable, reliable capacitor of relatively small.

Mica Capacitor

The mica capacitors are the low loss capacitors, used at high frequencies and this
capacitor is very stable chemically, electrically, and mechanically, because of its
specific crystalline structure binding & it is a typically layered structure. The most
common used are Muscovite and phlogopite mica. The Muscovite mica is better in
the electrical properties and the other Mica has a high-temperature resistance.

Paper Capacitor

The construction of paper capacitor is between the two tin foil sheet and they are
separated from the paper, or, oiled paper & thin waxed. The sandwich of the thin
foils and papers then rolled into the cylindrical shape and then it is enclosed into the
plastic capsule. The two thin foils of the paper capacitors attach to the external load.
 Paper Capacitor

In the initial stage if the capacitors the paper was used in between the two foils of the
capacitor, but these days the other materials like plastics are used, therefore it is
called as a paper capacitor. The capacitance range of the paper capacitor is from
0.001 to 2.000micro farad and the voltage is very high which is up to 2000V.

Film Capacitor

The film capacitors are also capacitors and they use a thin plastic as the dielectric.
The film capacitor is prepared extremely thin using the sophisticated film drawing
process. If the film is manufactured, it may be metalized depend on the properties of
a capacitor. To protect from the environmental factor the electrodes are added and
they are assembled.

Film Capacitor

There are different types of film capacitors are available like polyester film,
metallized film, polypropylene film, PTE film and polystyrene film. The core
difference between these capacitors types is the material used as a dielectric and
dielectric should be chosen properly according to their properties. The applications of
the film capacitors are stability, low inductance, and low cost.

The PTE film capacitance is a heat resistance and it is used in the aerospace and
military technology. The metalized polyester film capacitor is used in the applications
are it requires long stability at a relatively low.

Non-Polarized Capacitors

The nonpolarized capacitors are classified into two types plastic foil capacitor and
the other one is the electrolytic nonpolarized capacitor.
 Non-Polarized Capacitor

The plastic foil capacitor is non-polarized by nature and the electrolytic capacitors
are generally two capacitors in the series, which are in the back to back hence the
result is in the non-polarized with half capacitance. The nonpolarized capacitor
requires the AC applications in the series or in parallel with the signal or power
supply.

The examples are the speaker crossover filters and power factor correction network.
In these two applications, a large AC voltage signal is applied across the capacitor.

Ceramic Capacitor

The ceramic capacitors are the capacitors and use the ceramic material as a
dielectric. The ceramics are one of the first materials to use in the production of
capacitors as an insulator.

Ceramic Capacitor

There are many geometries are used in the ceramic capacitors and some of them
are the ceramic tubular capacitor, barrier layer capacitors are obsolete because of
their size, parasitic effects or electrical characteristics. The two common types of
ceramic capacitors are multilayer ceramic capacitor (MLCC) and ceramic disc
capacitor.

The multilayer ceramic capacitors are prepared by using the surface mounted (SMD)
technology and they are smaller in size, therefore, it is used widely. The values of
the ceramic capacitors are typically between the 1nF and 1µF and the values are up
to 100µF are possible.

The ceramic disc capacitors are manufactured by coating a ceramic disc with silver
contacts on both sides and to achieve with the larger capacitance, these devices are
made from multiple layers. The ceramic capacitors will a have high-frequency
responses due to the parasitic effects like resistance and inductance.

A parallel plate capacitor is a device that can store electric charge and
energy in the form of an electric field between two conductive plates. The
plates are separated by a small distance and are connected to a voltage
source, such as a battery. The space between the plates can be filled with
air, a vacuum, or a dielectric material, which is an insulator that can be
polarized by an electric field.

What is a Parallel Plate Capacitor?

A parallel plate capacitor is defined as an arrangement of two metal plates
of equal area A and opposite charge Q, separated by a distance d. The
plates are connected to a voltage source V, which creates an electric
potential difference between them. The electric field E between the plates is
uniform and perpendicular to the plates, as shown in Figure 1.

The electric field E between the plates is given by:

where V is the voltage across the plates, d is the separation between the
plates, σ is the surface charge density on each plate, and ϵ0 is the
permittivity of free space.
The electric field E induces a polarization P in the dielectric material, which
is the dipole moment per unit volume of the material. The polarization P
reduces the effective electric field E inside the dielectric and increases the
capacitance C of the capacitor.

The capacitance C of a parallel plate capacitor is the ratio of the charge Q

on each plate to the voltage V across the plates:

The capacitance C depends on the geometry of the plates and the dielectric
material between them. For a parallel plate capacitor with air or vacuum
between the plates, the capacitance C is given by:

where A is the area of each plate and d is the separation between the plates.

For a parallel plate capacitor with a dielectric material between the plates,
the capacitance C is given by:
where k is the relative permittivity or dielectric constant of the material,
which is a dimensionless quantity that measures how easily the material
can be polarized by an electric field.

The relative permittivity k of a dielectric material is always greater than or

equal to 1. The higher the value of k, the more charge can be stored on the
capacitor for a given voltage, and thus the higher the capacitance.

Applications of Parallel Plate Capacitors

Parallel plate capacitors have many applications in various fields of science
and engineering. Some of them are:

 Filtering: Parallel plate capacitors can be used to filter out unwanted

frequencies or noise from an electrical signal. For example, they can
block direct current (DC) signals and allow alternating current (AC)
signals to pass through. They can also be used to smooth out voltage
fluctuations in power supplies.
 Tuning: Parallel plate capacitors can be used to tune electrical
circuits to resonate at a desired frequency. For example, they can be
used in radios, televisions, and other communication devices to select
a specific channel or frequency band.
 Sensing: Parallel plate capacitors can be used to sense physical
quantities such as pressure, temperature, humidity, displacement,
etc. For example, they can be used in microphones, thermometers,
hygrometers, accelerometers, etc. The capacitance of a parallel plate
capacitor changes with these physical quantities due to changes in
the distance between the plates or the dielectric material between
them.
 Energy storage: Parallel plate capacitors can be used to store
electrical energy in their electric fields. For example, they can be used
in flashlights, cameras, defibrillators, etc. The energy stored in a
parallel plate capacitor is given by:
 where U is the energy stored in joules (J), C is the capacitance in farads (F),
and V is the voltage in volts (V).

Mutual inductance

Mutual inductance is the effect of one coil's magnetic field on another coil's
magnetic field. It's the basic operating principle of transformers, motors,
generators, and other electrical components that interact with another
magnetic field.

MADPCB

Here's how mutual inductance works:

1. Bring two coils of wire close together so that the magnetic field from one links with
the other.
2. The magnetic field in one of the coils tends to link with the other.
3. This leads to the generation of voltage in the second coil.
4. The current flowing in one coil induces a voltage in an adjacent coil.
Mutual inductance is the basis of eddy current inspection. Any electrically
conductive object will conduct an induced current if it is placed in a
changing magnetic field
 What is a DC Motor?
A direct current (DC) motor is a type of electric machine that converts
electrical energy into mechanical energy. DC motors take electrical power
through direct current, and convert this energy into mechanical rotation.

DC motors use magnetic fields that occur from the electrical currents
generated, which powers the movement of a rotor fixed within the output
shaft. The output torque and speed depends upon both the electrical input
and the design of the motor.

Types of DC Motors
So far, this guide has broadly explained how DC motors work, the history of
these mechanisms, and what they look like. While the principles are the
same across variants, there are actually several different types of DC
motors, which offer specific advantages and disadvantages over each
other.

This section of the guide will look at the four main types of DC motor -
brushless, brushed, shunt, and series

Applications of DC motors
Thanks to the different types of DC motors available, there are a wide
variety of applications for DC motors. The previous section considered
some of the various applications and circumstances where DC motors are
used, and the benefits of the various types of motor.

While each type has its advantages, broadly speaking, there are various
uses of a DC motor. At home, small DC motors are used in tools, toys and
various household appliances. In retail, the applications of DC motors
include conveyors and turntables, while in an industrial setting, large DC
motor uses also include braking and reversing applications.

Here are a few more specific uses for DC motors:

DC motors for fans

Although fans traditionally use AC motors, there are an increasing number

of DC motor ceiling fans hitting the market. These fans are gaining in
popularity as they are far more economical than their AC equivalent, thanks
to the way in which they operate.

As we have learned in this guide, DC motors utilise magnetic fields to

process electrical energy into mechanical energy, and by using brushless
motors, DC motor ceiling fans can be operated from standard household
AC electricity. The only real downside to the DC motor fan is its cost, but
the energy savings easily offset this.

DC motors for pumps

Hydraulic pumps are an essential industrial tool, which are used in almost
all industries including: construction, mining, manufacturing, and steel. DC
motors are used to power these pumps because of their easy variable
speed control and excellent response when moving.

Like ceiling fans, the DC motor pump has also benefited from the
development of lower-cost brushless DC motors, which are far easier to
maintain on such a large industrial scope.

DC motors for toys

DC motors for toys are a popular choice for manufacturer and hobbyists,
with these ‘toy motors’ often used in children’s toys such as remote control
cars and model trains. Small DC motors work well in this setting, as they
are easy to use and extremely rugged.

The wide variety of voltages for DC motors means they can be used for
toys that require different speeds and movement types, and those that
need a DC motor with controller.

DC motors for electric cars

While there are a variety of different motor types used in electric cars, DC
motors for electric vehicles are widely used because of their energy
efficiency and durability.
In addition to professional manufacturers, many hobbyists and kit car
makers prefer large DC motors for their higher starting torque, particularly
series wound motors, and their variable speeds with voltage input.

DC motors for robots

'Robot’ is a broad term, but for many hobbyists and engineers, robots are
any electromechanical device designed to achieve a specific task. DC
motors for robots are used to ‘actuate’ something, such as tracks, arms, or
cameras, with this motor particularly popular for a number of reasons.

DC motors are particularly convenient, as they have high torque and

efficiency, making them ideally suited to robotics.

DC motors for bikes

Electric bikes are popular because they do not require a license, if the
maximum assisted speed is under 20 miles an hour. To ensure the power
levels and the torque needed, brushless DC motors are usually used for
electric bikes.

Electric bikes use a compact DC motor built into the hub of the back or
front wheel, or mounted in the centre of the bike and connected to the
pedal sprocket.

What is an Induction Motor?

A motor with only amortisseur windings is called an induction motor. An
induction motor is the most modest electrical machine from the construction
point of view, in the majority of the cases. The induction motor works on the
principle of induction where an electromagnetic field is induced into the
rotor when the rotating magnetic field of the stator cuts the stationary rotor.
Induction machines are by far the most common type of motor used in
industrial, commercial, or residential settings. It is a three-phase AC motor. Its
characteristic features are:

Applications
The applications of single phase induction motor are; it is used in low-power
applications and widely used in domestic applications as well as industrial.
And some of those are mentioned below
 Pumps
 Compressors
 Small fans
 Mixers
 Toys
 High-speed vacuum cleaners
 Electric shavers
 Drilling machines

Permanent Magnet Moving Coil or PMMC Instrument

Definition: The instruments which use the permanent
magnet for creating the stationary magnetic field between which
the coil moves is known as the permanent magnet moving coil or
PMMC instrument. It operates on the principle that
the torque is exerted on the moving coil placed in the field of the
permanent magnet. The PMMC instrument gives the accurate result
for DC measurement.
Construction of PMMC Instrument
The moving coil and permanent magnet are the main part of the PMMC
instrument. The parts of the PMMC instruments are explained below in
details.

Moving Coil – The coil is the current carrying part of the instruments
which is freely moved between the stationary field of the permanent
magnet. The current passes through the coil deflects it due to which the
magnitude of the current or voltage is determined. The coil is mounted
on the rectangular former which is made up of aluminium. The former
increases the radial and uniform magnetic field between the air gap of
the poles. The coil is wound with the silk cover copper wire between the
poles of a magnet.

The coil is mounted on the rectangular former which is made up of

aluminium. The former increases the radial and uniform magnetic field
between the air gap of the poles. The coil is wound with the silk cover
copper wire between the poles of a magnet.

Magnet System – The PMMC instrument using the permanent magnet

for creating the stationary magnets. The Alcomax and Alnico material
are used for creating the permanent magnet because this magnet has
the high coercive force (The coercive force changes the magnetisation
property of the magnet). Also, the magnet has high field intensities.

Control – In PMMC instrument the controlling torque is because of the

springs. The springs are made up of phosphorous bronze and placed
between the two jewel bearings. The spring also provides the path to the
lead current to flow in and out of the moving coil. The controlling torque
is mainly because of the suspension of the ribbon.

Damping – The damping torque is used for keeping the movement of

the coil in rest. This damping torque is induced because of the
movement of the aluminium core which is moving between the poles of
the permanent magnet.

Pointer & Scale – The pointer is linked with the moving coil. The pointer
notices the deflection of the coil, and the magnitude of their deviation is
shown on the scale. The pointer is made of the lightweight material, and
hence it is easily deflected with the movement of the coil. Sometimes the
parallax error occurs in the instrument which is easily reduced by
correctly aligning the blade of the pointer.

Advantages of PMMC Instruments

The following are the advantages of the PMMC Instruments.

1. The scale of the PMMC instruments is correctly divided.

2. The power consumption of the devices is very less.
3. The PMMC instruments have high accuracy because of the high
torque weight ratio.
4. The single device measures the different range of voltage and
current. This can be done by the use of multipliers and shunts.
5. The PMMC instruments use shelf shielding magnet which is useful
for the aerospace applications.
Disadvantages of PMMC Instruments

The following are the disadvantages of the PMMC instruments.

 1. The PMMC instruments are only used for the direct current. The
alternating current varies with the time. The rapid variation of the
current varies the torque of the coil. But the pointer can not follow the
fast reversal and the deflection of the torque. Thus, it cannot use for
AC.
2. The cost of the PPMC instruments is much higher as compared to
the moving coil instruments.
The moving coil itself provides the electromagnetic damping. The
electromagnetic damping opposes the motion of the coil which is
because of the reaction of the eddy current and the magnetic field.

What is Ohm’s Law?

Ohm’s law states that the electrical current flowing through any conductor
is directly proportional to the potential difference (voltage) between its
ends, assuming the physical conditions of the conductor do not change.
In other words, the ratio of potential difference between any two points of
a conductor to the current flowing between them is constant, provided the
physical conditions (e.g., temperature etc.) do not change.

Mathematically, Ohm’s law can be expressed as,

Introducing the constant of proportionality, the resistance R in the above

equation, we get,

Where,
  R is the resistance of the conductor in Ohm ( ),
 I is the current through the conductor in Amperes (A),
 V is the voltage or potential difference measured across the
conductor in Volts (V).

Ohm’s law is applicable to both DC and AC.

The relationship between the potential difference or voltage (V), the current
(I) and the resistance (R) in an electrical circuit was first discovered by the
German physicist George Simon Ohm.
The unit of resistance is Ohm ( ) was named in honour of George Simon
Ohm.

How Does Ohm’s Law Work?

As per the definition of Ohm’s law, the current flowing through a

conductor or resistor between two points is directly proportional to the
difference in voltage (or potential difference) across the conductor or
resistor.
But… that can be a bit difficult to understand.

So let’s get a better intuitive sense for Ohm’s Law by using some analogies.