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Series and Parallel Circuits

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Subido el 7 de noviembre de 2013 por Samuel E.

20 visualizaciones

Mr. Andersen contrasts series and parallel electrical circuits. A simulation is used to visualize electron flow through both circuit types.

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Hi. It's Mr. Andersen and today I'm going to be talking about series and parallel circuits. 00:00:00
These are a couple of different circuit diagrams. Remember this stands for a battery and each 00:00:11
of those stand for a resistor. And so this would be a series circuit. Remember it's a 00:00:15
closed circuit. So there's a loop where electricity can flow the whole way around. And then we 00:00:19
have three resistors. And so the electricity that goes through this has to go through these 00:00:24
as well. If we look at this one, this is one battery connected to three resistors as well. 00:00:29
But they're parallel to one another. In other words there's three loops that that electricity 00:00:34
can take. And so we call that a parallel circuit. Now the first time you look at a series in 00:00:39
a parallel circuit when it's actually connected there's some stuff that's not super intuitive. 00:00:45
In other words there's some weird stuff that takes place. But once you really understand 00:00:49
what's going on in both a series and a parallel circuit you'll do much better. And so today 00:00:53
I want to show you basically a parallel and a series circuit. A few demonstrations. And 00:00:58
I'm going to be using the circuit construction kit. This is at phet.colorado.edu. And I 00:01:05
would encourage you to go there and play around with it. It's the best way to learn about 00:01:11
electricity is to actually play around with it. Okay. So right here we've got two different 00:01:14
loops. This one is a, so this would be a battery right here. It's a 9 volt battery. This is 00:01:19
an ammeter which is going to measure the amps. We've then got wires connected to a light 00:01:24
bulb, back to a switch and then back to the battery again. And so this would be a series 00:01:28
circuit because electricity is going to flow in this direction through the battery and 00:01:32
then back, through the bulb and then back again. And so when I turn it on we can see 00:01:35
that electrons are flowing. We've got 0.9 amps and then it's running through a light 00:01:40
bulb. And so these rays around the outside of the light bulb show you how much light 00:01:45
is being given off from that. And so the first thing I'd like to do, let me turn that off 00:01:49
for just a second. So let me open that circuit for a second. Is kind of get a sense for how 00:01:54
much electricity is coming out or how much current is flowing through there and how much 00:01:59
light are we getting off of that. And now I'm going to add another light bulb. And I'm 00:02:02
going to put it in series. So let me add another light bulb here. And I have to break this, 00:02:07
split the junction. Connect to both sides of that. And let me move it down so it looks 00:02:13
a little better. Okay. So now we've got two light bulbs. We've got the same battery. You 00:02:21
kind of remember how much light we were getting at it before. And you remember the speed. 00:02:26
And so let's turn this one on now. Okay. So in a series circuit what we have now is those 00:02:30
two bulbs are not as bright. And the reason why, and if you remember how much speed we 00:02:37
were getting, how much current we were getting, remember it was 0.9 amps. And so in a series 00:02:44
circuit if we add more resistance we're going to decrease the amount of current. And as 00:02:50
a result we're going to have dimmer light bulbs. And so the current is going to be the 00:02:55
same through every component in a series circuit. And so the other thing about a series circuit 00:03:01
is let me try, let me remove this. So let me split the junction. Okay. So when I split 00:03:07
So when I split the junction there, I cut that wire and so it wasn't connected anymore. 00:03:14
And so both bulbs went out. And so the two things that you should learn, number one is 00:03:19
that in a series circuit all of them have to be working for current to flow. And the 00:03:23
second thing is that they all have the same amount of current. Volts is another thing. 00:03:29
And so let's add a voltmeter as well. So if we add a voltmeter, this is a 9 volt battery. 00:03:34
If I look on either side of the light bulb we'll find that the volts are 9 volts. If 00:03:40
I move this lead over here, this electrode over here, we find that it's 4.5 volts. And 00:03:46
then if I shift both of them to this side of that light bulb it's 4.5 as well. And so 00:03:52
the sum of the volt or the voltage drop between the two components in that are going to equal 00:04:00
the volts that we have for the whole thing. So it's 9 volts. But then each of those bulbs 00:04:06
is going to be a drop of 4.5 volts. So we have 9 volts and then we have 0 volts when 00:04:10
we get to the other side. So let's get rid of that volt meter. And let me turn this one 00:04:15
off. And so let's return that for a second. So get a sense of how much light we're getting 00:04:19
from these two light bulbs. And we have 0.45 amps. And now we're going to look down here 00:04:26
at a parallel circuit. And so a parallel circuit there are two parallel pathways. In other 00:04:32
words there's a wire that goes through this bulb and a wire that goes through this bulb. 00:04:37
And so when I turn this on there's a clear difference between the two. And the first 00:04:42
time I saw this it was totally confusing to me. In other words these two light bulbs are 00:04:48
as bright as that one light bulb was before when it wasn't in series. And so the first 00:04:54
thing that should stand out to you is that these two bulbs are as bright as that one 00:05:00
bulb when it was, before it was hooked up in series. And so another thing that's happening 00:05:05
is that we actually have way more amps moving through this. And so you can see that the 00:05:11
electrons are moving more quickly. And so the difference between a series circuit and 00:05:15
a parallel circuit is that the current is actually increased. Remember when we had, 00:05:21
go back and remove this and just connect it together. So remember here we had 0.9 amps 00:05:26
for one light bulb. But here we now have 1.8 amps. In other words the electricity is actually 00:05:33
flowing faster. Why is that? Well here there is the current of this thread. And there's 00:05:38
the current of this branch. And the two currents together are going to sum up to this current. 00:05:45
And so before when we were saying the voltage drop in each of those sums up to the voltage 00:05:52
of the battery, well in a parallel circuit those two pathways, in other words those two 00:05:57
currents are going to sum up to the current of the whole branch. Another thing that happens 00:06:01
in a parallel circuit, let's kind of remove this light bulb. And so remember when I removed 00:06:08
a series light bulb the whole thing went out. But in a parallel circuit when I remove one 00:06:14
of those light bulbs. The other one keeps moving. Now you should have seen that when 00:06:19
I removed that light bulb the amps dropped down to 0.9. And electricity isn't flowing 00:06:24
through this side. But by hooking it up this way we've now got electricity or a path for 00:06:29
electricity to go. When I was a kid I remember we had a string of light bulbs that were hooked 00:06:37
up in series. And it was the most annoying light bulb strand that you could have for 00:06:42
Christmas lights. Because if you ever had one bulb go out on a series circuit then the 00:06:47
whole thing was broken all the way down. So you had to search through that string of lights 00:06:53
until you found the one that was burned out. Now they use parallel circuits. And the reason 00:06:56
they do that is you don't get that drop in current with each bulb. And the other thing 00:07:01
is that you can have a break in one of the bulbs and the other ones are all going to 00:07:06
work. And so that's kind of an introduction to series and parallel circuits. Remember 00:07:10
in a series circuit the current is going to be the same through every part of that loop. 00:07:16
But in a parallel circuit it's going to be the sum of the two will be the sum of the 00:07:25
current through the whole of the circuit. And the voltage drop, if we add our voltmeter 00:07:29
in a parallel circuit, it's going to be the same along each thread. So remember this would 00:07:35
be a 9 volt on this pathway. But it's also going to be a 9 volt on this pathway. And 00:07:42
so you're not getting anything for free with a parallel circuit. You're actually going 00:07:50
to go through more energy using this setup than you would over here because you're actually 00:07:54
gathering more amps. So that's parallel and that's series circuit. And I hope that's helpful. 00:07:59
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Idioma/s:
en
Etiquetas:
EducaMadrid
Autor/es:
Bozeman Science
Subido por:
Samuel E.
Licencia:
Reconocimiento - No comercial - Compartir igual
Visualizaciones:
20
Fecha:
7 de noviembre de 2013 - 14:11
Visibilidad:
Público
Centro:
IES JOAQUIN ARAUJO
Duración:
08′ 04″
Relación de aspecto:
16:10 El estándar usado por los portátiles de 15,4" y algunos otros, es ancho como el 16:9.
Resolución:
576x360 píxeles
Tamaño:
24.94 MBytes

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