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okay this is the lab part of
the the divider and voltage drops
tutorial. What I've done here
is tabulated a whole bunch
values. So for example a
I've taken Rb here and
just set lots of different values
on the decade box when we run through this
now the 18k resistor
is actually a fixed resistor within the circuit
that's not going to change that's going to be fixed throughout so the anything's
going to change
are these Rb values. So as we change these values
then obviously the voltage drops across both of them
are going to change and I've used the
voltage divider formulas here plus ohms law to get all of this
ready to go so we've got all these
done ahead of time.
Wiring this circuit up we should see that these
calculated values actually match
the measured values if the measured values are close to these then we know
that the voltage divider formula is good
and that ohms law is good and that everything is as it should be.
if for some reason we don't get the same values
then the most likely scenario is that we've connected up circuit
incorrectly. So you can do this
simple circuit yourself it's just basically one resistor and a decade
box, very easy to set up
all we need here in the circuit is the
in-line ammeter
so basically you could use a multimeter
set too current mode a
I've used a single
voltmeter here and I've got a lead so I can drop between
the fixed resistor and drop it between the decade box
so that I can show you the the voltage drops
as we go through this. Obviously the whole things running on a fixed power
supply of 12 volts.
So let's have a look at the the the bits and pieces.
so what we've got is
the decade box which is for the
the resistor values, here I've already set it to be
18,000 ohms just to begin this with. Then
there is the the voltmeter
we're also using an AVO
Ammeter. So basically this is just an AVO meter
set to the current setting
at its lowest resolution so this is this is now set.
Hang on, I'll just make sure that this is set to the lowest resolution
so that's good.
what else have we got. Okay
this is actual circuit on the breadboard. Pretty nothing much going on
here
so I've connected up the decade box a
in here so it's in series with this fixed
resistor here. so this is
the only single component really on the breadboard
everything else is just connected wires. You've got wires connected to the Ammeter
and in line we've got a decade box
connected here and the voltmeter.
I'm using these two leads inserted like so,
so that I can use them when I swap between the resistors all I have to
do is pick them both out and into new connections
and then we get the voltage across both resistors like this
This just to make easy for you to see
Instead of using 2 meters is much nicer to see the
we're actually moving these across the resistor
she can actually see the change in the voltmeter and then read two different
voltage
drops. so this is all ready running at 12 volts as the
actual power supply is already on.
she's over there, so the power supply is actually on now.
So what I'm going to do is just basically just turn on the
the voltmeter case the ball meters on
now let's have a look at what we should be getting
so have a look at our results in so
18 wish said RB
this column we sell upbeat 18 where the arrow is there
now 18 obviously
both resist is all the same value so
twelve jewish for cool only getting a job six jewelsburg cool
across each of those so that that
fashion show six vaults on both those
and then when we look at the Amita we should see the current
is if you do I'm still always them 12
Suge I'm slowed using those
using 218 you get 36,000 you get twelve
divided by 36,000 gives you points 33
recurring so we should see the ammeter shows
points3 million amps so let's just check
first one then
okay so the vote so we've actually got the vote me a dropped course one of
those already in it any
to see showing exactly six votes so that's just me these over to the other
resistor I don't know which one is but it's the other one
not showing six shots as well i mean you know for
give or take a hundred a couple hundred votes
so so that's good that shows that this is a
probably connection up correctly so let's go through some the others now
just prove us
prove to yourself that the the these numbers actually
follow the actual measured patients what they transition
not that it really matters but to not see them on a sign there
so yet so there's a gonna have those like that
so let's have a look at maybe one of the others named
so why don't we just go where 18,000 for RB that's just
Senate 36,000 she's the bomb on their
when he said 36,000 should see the voltage across
Diego from 60 stance 24 volts
and then the voltage across BB and
which is the decade box batch will now which ones decade box
so that show I also sees me switch phone says a votes will know
its the one that's trucked across the decade box
when we checked the current should say should show
point2 millions would inject %ah
loss from birth will do that now just before we
a.m. just before we go stick just checking account so
we're gonna stay with where we were be on 18,000
and 18,000 on both this is given as six votes across both
so from all that should give us
looking at this point
3 millions let's just check that we've got so
he is the Amita right so now
a show with my fingers it might be difficult to see this but
where my finger is now that's a bow 3
points3 millions so if we see that needle flick
close to where my finger is at the moment batch tell us
so I'm just gonna switch that on
yeah and I can tell you looking at it I can see quite clearly that's
a point three sorry Miley amps so that's
absolutely spot-on that's good so let's go now to
36,000 which is the bottom one
so now we're gonna go to the 36,000
so will set the decade talks to 36,000 now
in
okay so we got 36,000 so that's a look what we've tabulated to
so for 36 that which is safe for an 8
so the voltage across the fixed
18k resist a *** show four bolts
so let's see on the other one show 8
but so now we know that leads that deets currently
all dropped across the deck a box cuz the kids a pulse
so that's so I would say now we can move over
have a look at the other on a fixed resistor
is showing for votes
which is exactly what we've what we what we've actually calculate
so that's good the faction preachers go back and show you that a gang
eight votes and
now let's have a look at what accounts for us to be
so the counts post to be point two million so I show that much finger
point2 is where my way finger is there now
so that's if you see that needle that neither should move to bat with my
finger ish
to keeping our eye dropdown
just show you a point to
is a game that's their just
have a look at the knees are going
okay said that showing point2
324 so that's
pretty close now let's look its
another one just double check okay we'll go with the
any action last video we showed 6,000
hate 18,000 so that's do that one now switches that one
in the middle age say six 6,000 if we had six thousand
18,000 a total resistance which is twenty four thousand
which is C nine votes across fixed resistor
and three votes across the decade books
and account should show point five million homes
so let's just check back so we can a setback to
6,000 now
switches 0 sub-zero
and thats showing six thousand now
so see what the vote lisa says
that showing more or less three votes what was the other one
I am the other was shown on sofa remove these elites
over we should see nine appear on that'll teach
told me to they go news to me
nine votes so which confirm that
all these numbers is so far correct and obviously that they're going to be
correct for the rest of them as well
that's just checked the con
but the county's point five million amps so to show you that when my finger
that should that needle should now
go to NY finger is now that nato should go right up to their
need it was there at the moment Sri to see that
and if the count shows point five million
the needle needs to go there as as without calculation so that's a
check that
yet you can see me for a second six see
they go that's Sakshi on point five million amps
so they go so all these numbers
actually confirmed all of our calculations
the the experimental numbers are identical
so there we go we know that
these voltage divider work
we know that Holmes was good everything works
everything is as it should be so
this is a good experiment if you do this she get a nice fit
feeling because you can see you get good confirmation when you actually do the
real thing
and it's really nice to seen the numbers actually matchup
when you do an experiment search although it might seem
very am simple
a what is a very simple circuit
but don't let that put you off the destiny give it a go
because when you start if you measure luck said the voltage drops across the
two
resistance and then you know actually calculate the count calculate
the voltages then when when these numbers match up
you'll you'll your you'll actually learn a lot by just doing this
me so very well using software packages to emulate things
the really don't get it doesn't really sink in as well as when you actually
physically build a
and do it and that's pretty simple bill that takes five minutes to build one in
these
you don't need to use all these
bits and pieces on using you can get a really cheap multimeter
you need to use decade box just going up a whole bunch
resistors I mean I've any use decade box is easier
be just lie not whole bunch positions along the breadboard there
and just any like this this this experiment and
do it I mean even if you've got a really cheap multimeter ill still be within
you know 100 also ill still
be reasonably accurate them to give it a go anyway
on the next the tutorial I'm gonna go over
tendons the room that's a nice the
a nice thing a nice strategy TA's when you wanna
join up different the
March modules if you like you wanna join a different bases circuits
so the day match his
so wat we're heading towards impedance matching here
so before we gain T at discussing a law banning paid in smashing
we go over that Annan's them first now
this what we've done in these last two videos about
voltage dividers and voltage drops leads really nicely into evidence there a
minute I'll make more sense if you
for if you now understand the voltage divided
and if you don this experiment as well okay thanks very much