/ News & Press / Video / How a Capacitor Works - Capacitor Physics and Applications

How a Capacitor Works - Capacitor Physics and Applications

WEBVTT
Kind: captions
Language: en

00:00:06.460 --> 00:00:11.940
Hello Dejan Nedelkovski here from
HowToMechatronics.com. In this tutorial we
00:00:11.940 --> 00:00:15.920
will learn what capacitor is, how it
works and take a look at some basic
00:00:15.929 --> 00:00:21.480
application examples. There is almost no
circuit which doesn't have a capacitor
00:00:21.480 --> 00:00:26.130
on it and along with resistors and
inductors there the basic passive
00:00:26.130 --> 00:00:32.040
components that we used in electronics.
A capacitor is a device capable of storing
00:00:32.040 --> 00:00:37.140
energy in a form of electric charge.
Compared to a same sized battery a
00:00:37.140 --> 00:00:42.450
capacitor can store much smaller amount
of energy, around ten thousand times
00:00:42.450 --> 00:00:47.930
smaller but useful enough for so many
circuit design. A capacitor is
00:00:47.930 --> 00:00:52.320
constructed out of two metal plates
separated by an insulating material
00:00:52.320 --> 00:00:57.239
called dielectric. The plates are
conductive and they are usually made of
00:00:57.239 --> 00:01:02.280
aluminum or other metals, while the
dielectric can be made of any kind of
00:01:02.280 --> 00:01:07.650
insulating material such as paper, glass,
ceramic or anything that obstructs the
00:01:07.650 --> 00:01:12.900
flow of the current. The capacitance of a
capacitor measured in Farads,
00:01:12.900 --> 00:01:17.580
is directly proportional to the surface
area of the two plates, as well as the
00:01:17.580 --> 00:01:21.930
permittivity of the dielectric. While the
smaller the distance between the plates
00:01:21.930 --> 00:01:26.580
the greater the capacitance. That being
said now let's take a look how a
00:01:26.580 --> 00:01:32.460
capacitor works. First we can note that a
metal typically has an equal amount of
00:01:32.460 --> 00:01:37.320
positively and negatively charged
particles which means it's electrically
00:01:37.320 --> 00:01:42.210
neutral. If we connect a power source or
a battery to the metal plates of the
00:01:42.210 --> 00:01:47.970
capacitors a current will try to flow or
the electrons from the plate connected
00:01:47.970 --> 00:01:52.500
to the positive lead of the battery
will start moving to the plate connected
00:01:52.500 --> 00:01:56.880
to the negative lead of the battery.
However, because of the dielectric
00:01:56.880 --> 00:02:02.100
between the plates the electrons won't
be able to pass through the capacitor so
00:02:02.100 --> 00:02:06.119
they will start accumulating on the
plate. After a certain number of
00:02:06.120 --> 00:02:10.740
electrons accumulated on the plate
the battery will have insufficient energy
00:02:10.740 --> 00:02:14.810
to push any new electronics
to enter the plate because of
00:02:14.810 --> 00:02:19.910
the repulsion of those electrons which
are already there. At this point the
00:02:19.910 --> 00:02:25.640
capacitor is actually fully charged. The
first plate has developed a net negative
00:02:25.640 --> 00:02:30.430
charge and the second plate has
developed an equal net positive charge
00:02:30.430 --> 00:02:35.180
creating an electric field with an
attractive force between them which
00:02:35.180 --> 00:02:39.830
holds the charge of the capacitor.
Let's take a look how the dielectric can
00:02:39.830 --> 00:02:45.350
increase the capacitance of a capacitor.
A dielectric contains molecules that are
00:02:45.350 --> 00:02:50.239
polar which means that they can change
their orientation based on the charges
00:02:50.239 --> 00:02:55.459
of the two plates. So the molecules align
themselves with the electric field in
00:02:55.459 --> 00:03:00.200
such a way enabling more electrons to be
attracted to the negative plate while
00:03:00.200 --> 00:03:05.780
repelling more electrons out of the
positive plate. So once the capacitor is
00:03:05.780 --> 00:03:10.640
fully charged if we remove the battery
it will hold the electric charge for a
00:03:10.640 --> 00:03:16.970
long time acting as energy storage.
Now if we shorten the two ends of the
00:03:16.970 --> 00:03:21.440
capacitor through a load a current
will start flowing through the load the
00:03:21.440 --> 00:03:25.820
accumulated electrons from the first
plate will start moving to the second
00:03:25.820 --> 00:03:31.489
plate until both place become back again
electrically neutral. So that's the
00:03:31.489 --> 00:03:35.180
basic working principle of a capacitor
and now let's take a look at some
00:03:35.180 --> 00:03:39.829
application examples. Decoupling
capacitors or bypass capacitors are
00:03:39.829 --> 00:03:45.170
typical example. Decoupling capacitors
are often used along with integrated
00:03:45.170 --> 00:03:49.250
circuits and they are placed between the
power source and the ground of the IC.
00:03:49.250 --> 00:03:54.890
Their job is to filter any noise in the
power supply like voltage ripples which
00:03:54.890 --> 00:03:59.780
occur when the power supply for a very
short period of time drops its voltage
00:03:59.780 --> 00:04:04.850
or when a portion of a circle is switch
causing fluctuations in the power supply.
00:04:04.850 --> 00:04:09.709
At that moment when the voltage drop
occurs the capacitor will temporarily
00:04:09.709 --> 00:04:15.530
act as a power supply bypassing the main
power supply. Another typical examples
00:04:15.530 --> 00:04:21.979
are capacitors used in DC adapters.
For converting the AC voltage into a DC
00:04:21.979 --> 00:04:25.389
voltage a diode rectifier is usually
used, but
00:04:25.389 --> 00:04:30.460
without the help of capacitors it won't
be able to do the job. The output of a
00:04:30.460 --> 00:04:35.770
rectifier is a waveform so while the
output of the rectifier rises the
00:04:35.770 --> 00:04:40.990
capacitor charges and while the output
of the rectifier declines the capacitor
00:04:40.990 --> 00:04:46.569
discharges and in that way smooth the DC
output. Signal filtering is another
00:04:46.569 --> 00:04:51.069
application example of capacitors.
Because of their specific response time
00:04:51.069 --> 00:04:55.960
they are able to block low frequency
signals while allowing higher frequency
00:04:55.960 --> 00:05:00.849
to pass through. This is used in radio
receivers for tuning out undesired
00:05:00.849 --> 00:05:05.860
frequencies and in crossover circuits
inside speakers for separating the low
00:05:05.860 --> 00:05:09.750
frequencies for the sub-woofer and the
higher frequencies for the twitter.
00:05:09.750 --> 00:05:15.490
Another rather obvious use of capacitors
is for energy storage and supply.
00:05:15.490 --> 00:05:20.050
Although they can store considerably
lower energy compared to the same sized
00:05:20.050 --> 00:05:24.279
battery their lifespan is much better
and they are capable of delivering
00:05:24.279 --> 00:05:29.199
energy much faster which makes them more
suitable for applications where high
00:05:29.199 --> 00:05:34.750
burst of power is needed. So that would
be all for this tutorial but you can
00:05:34.750 --> 00:05:40.029
always find more details and tutorials
on my website HowToMechatronics.com.
00:05:40.029 --> 00:05:44.430
thanks for watching and don't forget to
subscribe

Sales phone