Capacitor is a
device that is desighned to storage electrical charges and release it to the
circut as it is required. Capacitors are used in a lot of electronic circuits
to perform variety oftasks.
Def: capacitor is a device that can
store the electric charge, this cause a potential difference across its plate. So,
the capacitor is like a battery that can be charge. Unit of capacitance is farad
The capacitors are made of two
plates separated by a dielectric insulated material.
Capacitor can be use in parallel and
series circuit, and both have pros and cons.
For the parallel circuit the voltage
across the circuit will be same but the current (Q) will be different.
For series circuit (Q) will be the same accrues the circuit but (V)
will be different.
The pros of using parallel circuit is that if one of the capacitor
stop working the circuit will continue working.
In series circuit if one of the
capacitor is stop working the whole circuit will stop working.
The main equations that we use to
determinate the value of capacitance for the parallel plate capacitor is:
Q=CV C=Q/V V=Q/C C=?A/d
Where (Q) is the charge on each
conductor, (V) is the potential Difference between the conductors, (C) is the
capacitance of the capacitor, (?) is the permittivity in the space = 8.85*10-12
f/m, (A) is the capacitor area.
For the spherical capacitor we can
determinate the capacitance by:
C=4?? (ra rb/ra+rb)
Where ra & rb are the shell radius of the inner and outer sphere.
Also, we can determinate the
electric field between the conducting plate by:
Energy stored in capacitor= 0.5*CV2
or 0.5 QV
Work for the capacitor= Q2
Dielectric constant (K) =C/C0
For series capacitor combination (Ceq)
= C1 C2/ C1 +C2
For parallel capacitor combination
(Ceq) = C1 +C2 +….
Energy density (u) = 0.5* ?0*E2
Permittivity (?) = K*?0
Dielectric filling in spherical
capacitor(c) = 4*?* ?0 *ra*rb/ rb-ra
Type of capacitor
There are many types of capacitors
depending on where they are used:
capacitor: this type of capacitor gained it’s named
because it uses a ceramic dielectric. The pros of using this capacitor is that
it has a low loss factor and high level of stability. Ceramic capacitors are generally
the top most of the other types and therefore can be used in a vast range of
application. Range of capacitance is from a few Pico- farads up to values
around 0.1 µF.
capacitor: it is the
most popular capacitor type because it can storage capacitance more than 1 µF.
Plastic film capacitor: it has two main formats, Metallised film and Film foil. Each has its own properties, allowing
them to be used in specific applications.
capacitor: In applications where size is
important, tantalum capacitors can be used.
Silver Mica capacitor:
silver mica capacitor is not common used these days. But they are
still available, if the value of stability is paramount and low losses are
Super cap capacitor: this capacitor starts to become customary type, they are too large for use in most circuits and
their frequency response is limited.
Finally: capacitor has different
type with different capacitance size, so they can fit in any electrical job.
Application of using capacitor
Energy: in some cases, like in the flash of a camera you need a build-up of
energy and then a sudden release, here come the advantage of using capacitor
because it can storage energy then release it. Once
it has reached the peak level, the capacitor discharges, causing a flash.
Smoothing changes in voltage: it can smooth circuit in AC adaptor.
By using capacitor
the will become
as Sensors: Capacitors are used as sensors to
measure a variety of things, including air humidity, also for the car, they
help the driver to parking safely.
Capacitors for Signal
Processing: Capacitors have found increasingly
advanced applications in information technology. Dynamic Random-Access Memory
(DRAM) devices use capacitors to represent binary information as bits.
blocking capacitor: In this application the capacitor
blocks the passage of DC current (after completely charged) and yet allows the
AC to pass at certain portion of a circuit.
low pass filter: low frequencies is upper at the
output, and high frequencies are cut off.
is a lot of application for using the capacitor in real life but, one type of
capacitor may not be suitable for all applications.