How CAPACITORS Work (ElectroBOOM101-006)

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00:00:00.000
hi it is time for you to learn about the
00:00:03.020 00:00:03.030 basic components well I've already told
00:00:06.320 00:00:06.330 you about resistors a while back so all
00:00:08.270 00:00:08.280 is left is capacitors and inductors
00:00:09.850 00:00:09.860 there are quite simple really
00:00:12.379 00:00:12.389 and I won't dive too deep I promise the
00:00:15.589 00:00:15.599 capacitor theory is quite simple really
00:00:18.019 00:00:18.029 atoms have cores and electrons that turn
00:00:20.570 00:00:20.580 around them electrons have negative
00:00:22.609 00:00:22.619 charge while cores have protons that are
00:00:24.800 00:00:24.810 positive opposing charges attract each
00:00:27.259 00:00:27.269 other while the same charges repel each
00:00:29.419 00:00:29.429 other
00:00:29.720 00:00:29.730 all thanks to electric fields that's all
00:00:32.150 00:00:32.160 you need to know for now and it bit more
00:00:34.250 00:00:34.260 see you can't just shove an electron
00:00:36.440 00:00:36.450 into a conductor because there is no
00:00:38.150 00:00:38.160 room and they repel each other and push
00:00:40.069 00:00:40.079 back unless you bribed them with some
00:00:42.410 00:00:42.420 positive charge like get into yourself
00:00:44.869 00:00:44.879 dad I'm not getting in there are you
00:00:48.410 00:00:48.420 afraid I'm not afraid I can't stand this
00:00:50.630 00:00:50.640 guy I'll tear it apart you don't want
00:00:52.790 00:00:52.800 these blood on my hands the cell beside
00:00:54.979 00:00:54.989 you is filled with girls hello there
00:00:58.959 00:00:58.969 okay I go in there or like imagine
00:01:01.310 00:01:01.320 hackers work alone unless you are a
00:01:03.560 00:01:03.570 great target and they all work together
00:01:05.509 00:01:05.519 to steal your data
00:01:06.890 00:01:06.900 take it away James that's why you should
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00:01:27.620 00:01:27.630 to you Mary
00:01:28.190 00:01:28.200 I made a plexiglass container with a
00:01:31.249 00:01:31.259 thin gap between the surfaces and fill
00:01:33.740 00:01:33.750 it with no d-mail magnets with the same
00:01:35.960 00:01:35.970 direction so they repel each other I
00:01:37.819 00:01:37.829 learned it from Cody's lab now imagine
00:01:40.399 00:01:40.409 these are electrons repelling each other
00:01:42.319 00:01:42.329 let's assume this is the neutral state
00:01:44.539 00:01:44.549 of a conductor and electrons and protons
00:01:46.429 00:01:46.439 are equal and we can't fit any more
00:01:48.590 00:01:48.600 electrons in there like there is five
00:01:51.020 00:01:51.030 electrons on this side now imagine this
00:01:53.330 00:01:53.340 magnet is a positive ion core stripped
00:01:55.700 00:01:55.710 of its electrons if we bring this
00:01:57.620 00:01:57.630 positive charge to our electrons it
00:01:59.600 00:01:59.610 pulls them close to each other so now
00:02:01.999 00:02:02.009 there is more room on that surface and
00:02:04.130 00:02:04.140 more electrons can fit there like six
00:02:06.319 00:02:06.329 now and that's how capacitors work you
00:02:08.779 00:02:08.789 have two conductive surfaces overlapping
00:02:11.330 00:02:11.340 but
00:02:11.750 00:02:11.760 not cutting isolated by a nonconductor
00:02:14.089 00:02:14.099 called a dielectric that can be air or
00:02:16.880 00:02:16.890 better and now if you put a power supply
00:02:19.280 00:02:19.290 across the surfaces like a battery you
00:02:21.890 00:02:21.900 can push electrons into one surface and
00:02:24.470 00:02:24.480 suck them from the other surface of
00:02:26.360 00:02:26.370 course the electric current is defined
00:02:28.460 00:02:28.470 as the reverse of the flow of electrons
00:02:30.649 00:02:30.659 the electric force between these charges
00:02:33.920 00:02:33.930 keeps them together so even when you
00:02:36.710 00:02:36.720 disconnect the battery the capacitor
00:02:38.960 00:02:38.970 keeps its charge and just like that you
00:02:41.630 00:02:41.640 can charge a capacitor of course it only
00:02:43.699 00:02:43.709 takes a fraction of a second to charge
00:02:45.619 00:02:45.629 which depends on dama right connects it
00:02:51.740 00:02:51.750 backwards I think I did you would think
00:02:54.890 00:02:54.900 having two conductors side by side
00:02:56.750 00:02:56.760 wouldn't care about the voltage polarity
00:02:58.509 00:02:58.519 which is true for some capacitor types
00:03:01.220 00:03:01.230 like ceramic but apparently in some like
00:03:03.740 00:03:03.750 electrolytic it matters see capacitors
00:03:06.410 00:03:06.420 are made with different structures like
00:03:08.300 00:03:08.310 ceramic electrolytic tantalum or others
00:03:11.000 00:03:11.010 and each one has its own pros and cons
00:03:13.099 00:03:13.109 the chemistry and structure of some of
00:03:15.530 00:03:15.540 them like electrolytic or tantalum makes
00:03:17.990 00:03:18.000 them polarized it's like having a very
00:03:20.509 00:03:20.519 fluid across your capacitor as soon as
00:03:23.150 00:03:23.160 you put reverse voltage or too much
00:03:25.099 00:03:25.109 positive voltage across your capacitor
00:03:26.990 00:03:27.000 it starts conducting extra current and
00:03:29.539 00:03:29.549 blows up which makes for great
00:03:31.789 00:03:31.799 pyrotechnics let's look at it again
00:03:34.500 00:03:34.510 [Music]
00:03:50.400 00:03:50.410 in any case a charged capacitor has this
00:03:53.920 00:03:53.930 potential energy in it where the charges
00:03:56.260 00:03:56.270 like to get together but they can't
00:03:58.090 00:03:58.100 because of the dielectric and are held
00:04:00.160 00:04:00.170 in position by the attracting electric
00:04:02.650 00:04:02.660 fields but as soon as you put a load
00:04:04.990 00:04:05.000 across it the charges say you can stop
00:04:08.290 00:04:08.300 our love now there's a new way you
00:04:13.540 00:04:13.550 wasn't burden tell me about it so well I
00:04:25.300 00:04:25.310 didn't care what I can't just let things
00:04:27.460 00:04:27.470 penetrate me so the charges passed
00:04:30.760 00:04:30.770 through the load and the capacitor
00:04:33.010 00:04:33.020 discharges now you might ask why would
00:04:35.590 00:04:35.600 we need solid dielectrics between plates
00:04:38.140 00:04:38.150 instead of air there are three good
00:04:40.150 00:04:40.160 reasons one is that they make sure
00:04:42.070 00:04:42.080 plates won't touch second is that they
00:04:45.610 00:04:45.620 can isolate against leakage and arcing
00:04:48.219 00:04:48.229 much better than air so you can bring
00:04:50.320 00:04:50.330 the place much closer and third similar
00:04:53.680 00:04:53.690 to ferromagnetic material that we make
00:04:55.630 00:04:55.640 our inductor and transformer cores from
00:04:58.180 00:04:58.190 because they improve magnetic fields
00:05:00.490 00:05:00.500 good dielectrics also improve electric
00:05:03.310 00:05:03.320 fields based on their electric
00:05:05.110 00:05:05.120 permittivity and result in higher
00:05:07.210 00:05:07.220 capacitance now you might ask what's a
00:05:09.400 00:05:09.410 good reason to bring the plates as close
00:05:11.469 00:05:11.479 as possible well the electric forces
00:05:13.990 00:05:14.000 between charges is very small over long
00:05:16.600 00:05:16.610 distances so we have to bring them close
00:05:19.090 00:05:19.100 for increased attraction and that
00:05:21.029 00:05:21.039 increases the amount of charges we can
00:05:23.409 00:05:23.419 put in a capacitor and so increases its
00:05:25.870 00:05:25.880 capacity but too high of a voltage over
00:05:28.330 00:05:28.340 too small of a gap will break the
00:05:30.400 00:05:30.410 dielectric and short the plates that's
00:05:32.740 00:05:32.750 why every capacitor has a specific
00:05:34.930 00:05:34.940 voltage rating and also the larger the
00:05:37.480 00:05:37.490 plates the more charges can fit in them
00:05:39.790 00:05:39.800 and so the higher the capacitance so the
00:05:42.430 00:05:42.440 capacitance is equal to epsilon which is
00:05:44.650 00:05:44.660 a constant for dielectric permittivity
00:05:46.950 00:05:46.960 times the area of the overlapping plates
00:05:49.960 00:05:49.970 divided by their distance
00:05:51.730 00:05:51.740 the unit of capacitance is ferret named
00:05:54.100 00:05:54.110 after Michael Faraday and the amount of
00:05:56.230 00:05:56.240 charge in coulombs you can put in a
00:05:58.240 00:05:58.250 capacitor is equal to its capacity
00:06:00.730 00:06:00.740 hands times the voltage across it so
00:06:02.980 00:06:02.990 more voltage or more capacity means more
00:06:05.770 00:06:05.780 charge now you might have heard some
00:06:07.689 00:06:07.699 idiots say that when there is a DC
00:06:09.790 00:06:09.800 signal like this it hits the capacitor
00:06:12.249 00:06:12.259 plates like this and gets blocked while
00:06:15.219 00:06:15.229 an AC signal can zigzag between the
00:06:17.620 00:06:17.630 plates like this and pass through well
00:06:21.730 00:06:21.740 that's wrong when you place a DC voltage
00:06:23.559 00:06:23.569 across a capacitor the voltage across it
00:06:26.589 00:06:26.599 rises as the charges flow into it until
00:06:31.089 00:06:31.099 the electric field in the capacitor is
00:06:33.490 00:06:33.500 the same as the field in the battery and
00:06:35.589 00:06:35.599 their voltages are equal and as you know
00:06:37.870 00:06:37.880 like temperature the electric current
00:06:40.360 00:06:40.370 only flows from a higher voltage to a
00:06:42.520 00:06:42.530 lower voltage and if the voltages on
00:06:44.649 00:06:44.659 both sides are the same then there is no
00:06:46.570 00:06:46.580 current so when you connect the DC
00:06:48.730 00:06:48.740 across a capacitor it charges to the
00:06:50.890 00:06:50.900 same voltage and the current stops but
00:06:53.110 00:06:53.120 when you have AC you constantly raise
00:06:55.300 00:06:55.310 and lower the voltage which pushes and
00:06:57.909 00:06:57.919 pulls the charges in and out of the
00:06:59.740 00:06:59.750 capacitor so if you look at your
00:07:01.659 00:07:01.669 capacitor as a black box it looks like
00:07:03.999 00:07:04.009 that the electric current goes in one
00:07:06.129 00:07:06.139 side and out of the other side then
00:07:08.499 00:07:08.509 returns in the next cycle so from
00:07:11.080 00:07:11.090 outside it looks like an AC current is
00:07:13.839 00:07:13.849 passing through the component although
00:07:16.209 00:07:16.219 the actual charges never passed through
00:07:18.189 00:07:18.199 the capacitor and only accumulate on the
00:07:20.560 00:07:20.570 plates so that's the capacitors for you
00:07:23.740 00:07:23.750 now let me tell you some interesting
00:07:25.870 00:07:25.880 wisdom around what was it going to say
00:07:29.559 00:07:29.569 all right capacitor is like a cop
00:07:33.330 00:07:33.340 it's voltage rises as you pour charges
00:07:36.210 00:07:36.220 into it its voltage rises faster if you
00:07:39.510 00:07:39.520 pour more charges per second or more
00:07:42.270 00:07:42.280 currents into it this is when the
00:07:45.930 00:07:45.940 capacitor blows up although the current
00:07:48.510 00:07:48.520 through a capacitor can change instantly
00:07:51.510 00:07:51.520 the voltage across it can not jump from
00:07:54.720 00:07:54.730 one value to another because it would
00:07:57.900 00:07:57.910 mean in that moment of time the current
00:08:00.720 00:08:00.730 was Infinite
00:08:02.040 00:08:02.050 because some charge went into the
00:08:04.530 00:08:04.540 capacitor in no time and that just
00:08:07.650 00:08:07.660 doesn't happen in real life I told you
00:08:11.010 00:08:11.020 the charge in a capacitor is equal to
00:08:13.890 00:08:13.900 the voltage across it times its
00:08:15.990 00:08:16.000 capacitance so it kinda bit of change in
00:08:19.800 00:08:19.810 charge can change the voltage that
00:08:21.990 00:08:22.000 crosses by a tiny bit if you watch my
00:08:24.780 00:08:24.790 previous electro boom 101 episodes you
00:08:27.030 00:08:27.040 know that current is equal to the amount
00:08:29.219 00:08:29.229 of charge passing per second so in a
00:08:32.880 00:08:32.890 tiny bit of time only a tiny bit of
00:08:36.270 00:08:36.280 charge passes if we rearrange these we
00:08:39.690 00:08:39.700 see that the current through a capacitor
00:08:41.459 00:08:41.469 is equal to its capacitance times the
00:08:44.940 00:08:44.950 rate at which the voltage changes in
00:08:47.730 00:08:47.740 time voltage and current both being a
00:08:50.100 00:08:50.110 function of time well this is pretty
00:08:51.720 00:08:51.730 much all you need to know about
00:08:52.740 00:08:52.750 capacitors so for example if you shove a
00:08:55.380 00:08:55.390 constant current into the capacitor then
00:08:57.690 00:08:57.700 the rate of voltage change is constant
00:08:59.880 00:08:59.890 meaning that the voltage changes in a
00:09:02.070 00:09:02.080 straight line that's not straight tray
00:09:04.910 00:09:04.920 straight line never mind
00:09:07.950 00:09:07.960 or if your voltage changes like this in
00:09:10.020 00:09:10.030 time and you can approximate a piece of
00:09:12.150 00:09:12.160 it as a straight line then the slope of
00:09:14.490 00:09:14.500 that piece times the capacitance gives
00:09:16.980 00:09:16.990 you the approximate current that runs
00:09:18.900 00:09:18.910 through the capacitor between these two
00:09:20.670 00:09:20.680 points it's all so simple wink if you
00:09:23.610 00:09:23.620 have a sine wave voltage across a
00:09:25.200 00:09:25.210 capacitor then at zero crossing we have
00:09:27.960 00:09:27.970 the maximum voltage change a positive
00:09:30.450 00:09:30.460 rate here so we have a peak current
00:09:32.390 00:09:32.400 positive here and here we have a peak
00:09:35.670 00:09:35.680 negative current and at the peaks of
00:09:37.470 00:09:37.480 voltage the rate of voltage change is
00:09:39.540 00:09:39.550 zero and so the current is zero in these
00:09:42.390 00:09:42.400 spots so the current through the
00:09:44.910 00:09:44.920 capacitor
00:09:46.440 00:09:46.450 looks like this always leading the
00:09:48.870 00:09:48.880 voltage by 90 degrees okay we have had
00:09:51.390 00:09:51.400 enough for one episode I'll give you
00:09:53.010 00:09:53.020 more details as we go forward into
00:09:54.750 00:09:54.760 electro boom 101
00:09:56.130 00:09:56.140 next stop inductors so make sure to like
00:09:58.890 00:09:58.900 my videos and subscribe to my channel
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