hi it is time for you to learn about the
basic components well I've already told
you about resistors a while back so all
is left is capacitors and inductors
there are quite simple really
and I won't dive too deep I promise the
capacitor theory is quite simple really
atoms have cores and electrons that turn
around them electrons have negative
charge while cores have protons that are
positive opposing charges attract each
other while the same charges repel each
other
all thanks to electric fields that's all
you need to know for now and it bit more
see you can't just shove an electron
into a conductor because there is no
room and they repel each other and push
back unless you bribed them with some
positive charge like get into yourself
dad I'm not getting in there are you
afraid I'm not afraid I can't stand this
guy I'll tear it apart you don't want
these blood on my hands the cell beside
you is filled with girls hello there
okay I go in there or like imagine
hackers work alone unless you are a
great target and they all work together
to steal your data
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to you Mary
I made a plexiglass container with a
thin gap between the surfaces and fill
it with no d-mail magnets with the same
direction so they repel each other I
learned it from Cody's lab now imagine
these are electrons repelling each other
let's assume this is the neutral state
of a conductor and electrons and protons
are equal and we can't fit any more
electrons in there like there is five
electrons on this side now imagine this
magnet is a positive ion core stripped
of its electrons if we bring this
positive charge to our electrons it
pulls them close to each other so now
there is more room on that surface and
more electrons can fit there like six
now and that's how capacitors work you
have two conductive surfaces overlapping
but
not cutting isolated by a nonconductor
called a dielectric that can be air or
better and now if you put a power supply
across the surfaces like a battery you
can push electrons into one surface and
suck them from the other surface of
course the electric current is defined
as the reverse of the flow of electrons
the electric force between these charges
keeps them together so even when you
disconnect the battery the capacitor
keeps its charge and just like that you
can charge a capacitor of course it only
takes a fraction of a second to charge
which depends on dama right connects it
backwards I think I did you would think
having two conductors side by side
wouldn't care about the voltage polarity
which is true for some capacitor types
like ceramic but apparently in some like
electrolytic it matters see capacitors
are made with different structures like
ceramic electrolytic tantalum or others
and each one has its own pros and cons
the chemistry and structure of some of
them like electrolytic or tantalum makes
them polarized it's like having a very
fluid across your capacitor as soon as
you put reverse voltage or too much
positive voltage across your capacitor
it starts conducting extra current and
blows up which makes for great
pyrotechnics let's look at it again
[Music]
in any case a charged capacitor has this
potential energy in it where the charges
like to get together but they can't
because of the dielectric and are held
in position by the attracting electric
fields but as soon as you put a load
across it the charges say you can stop
our love now there's a new way you
wasn't burden tell me about it so well I
didn't care what I can't just let things
penetrate me so the charges passed
through the load and the capacitor
discharges now you might ask why would
we need solid dielectrics between plates
instead of air there are three good
reasons one is that they make sure
plates won't touch second is that they
can isolate against leakage and arcing
much better than air so you can bring
the place much closer and third similar
to ferromagnetic material that we make
our inductor and transformer cores from
because they improve magnetic fields
good dielectrics also improve electric
fields based on their electric
permittivity and result in higher
capacitance now you might ask what's a
good reason to bring the plates as close
as possible well the electric forces
between charges is very small over long
distances so we have to bring them close
for increased attraction and that
increases the amount of charges we can
put in a capacitor and so increases its
capacity but too high of a voltage over
too small of a gap will break the
dielectric and short the plates that's
why every capacitor has a specific
voltage rating and also the larger the
plates the more charges can fit in them
and so the higher the capacitance so the
capacitance is equal to epsilon which is
a constant for dielectric permittivity
times the area of the overlapping plates
divided by their distance
the unit of capacitance is ferret named
after Michael Faraday and the amount of
charge in coulombs you can put in a
capacitor is equal to its capacity
hands times the voltage across it so
more voltage or more capacity means more
charge now you might have heard some
idiots say that when there is a DC
signal like this it hits the capacitor
plates like this and gets blocked while
an AC signal can zigzag between the
plates like this and pass through well
that's wrong when you place a DC voltage
across a capacitor the voltage across it
rises as the charges flow into it until
the electric field in the capacitor is
the same as the field in the battery and
their voltages are equal and as you know
like temperature the electric current
only flows from a higher voltage to a
lower voltage and if the voltages on
both sides are the same then there is no
current so when you connect the DC
across a capacitor it charges to the
same voltage and the current stops but
when you have AC you constantly raise
and lower the voltage which pushes and
pulls the charges in and out of the
capacitor so if you look at your
capacitor as a black box it looks like
that the electric current goes in one
side and out of the other side then
returns in the next cycle so from
outside it looks like an AC current is
passing through the component although
the actual charges never passed through
the capacitor and only accumulate on the
plates so that's the capacitors for you
now let me tell you some interesting
wisdom around what was it going to say
all right capacitor is like a cop
it's voltage rises as you pour charges
into it its voltage rises faster if you
pour more charges per second or more
currents into it this is when the
capacitor blows up although the current
through a capacitor can change instantly
the voltage across it can not jump from
one value to another because it would
mean in that moment of time the current
was Infinite
because some charge went into the
capacitor in no time and that just
doesn't happen in real life I told you
the charge in a capacitor is equal to
the voltage across it times its
capacitance so it kinda bit of change in
charge can change the voltage that
crosses by a tiny bit if you watch my
previous electro boom 101 episodes you
know that current is equal to the amount
of charge passing per second so in a
tiny bit of time only a tiny bit of
charge passes if we rearrange these we
see that the current through a capacitor
is equal to its capacitance times the
rate at which the voltage changes in
time voltage and current both being a
function of time well this is pretty
much all you need to know about
capacitors so for example if you shove a
constant current into the capacitor then
the rate of voltage change is constant
meaning that the voltage changes in a
straight line that's not straight tray
straight line never mind
or if your voltage changes like this in
time and you can approximate a piece of
it as a straight line then the slope of
that piece times the capacitance gives
you the approximate current that runs
through the capacitor between these two
points it's all so simple wink if you
have a sine wave voltage across a
capacitor then at zero crossing we have
the maximum voltage change a positive
rate here so we have a peak current
positive here and here we have a peak
negative current and at the peaks of
voltage the rate of voltage change is
zero and so the current is zero in these
spots so the current through the
capacitor
looks like this always leading the
voltage by 90 degrees okay we have had
enough for one episode I'll give you
more details as we go forward into
electro boom 101
next stop inductors so make sure to like
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