In this video, I'm going to explain to you why wires are twisted.
At the end of the video, I'll show you a really cool experiment that will help you visualize
what's going on.
But if this is our first time meeting, welcome.
My name is Kyle.
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The twisted pair of wires is a technology patented all the way back in 1881 by Alexander
Graham Bell.
There are two primary goals of this technology.
To prevent incoming noise and to prevent outgoing noise.
You see, with electricity there are two big problems.
Any time you run an electrical current through a wire a magnetic field is created around
that wire.
The reverse is also true.
Any time a magnetic field passes by a wire, it will induce an electrical current onto
that wire.
How does twisting the wires of a circuit help protect the signal on that circuit from noise?
Well remember that any circuit is made up of two wires - each with opposite energy.
So if there's a positive voltage on the black wire, there will be a negative voltage on
the red wire - and vice versa.
The polarity of the electrical current through each wire is opposite and the polarity of
the magnetic field is also opposite.
When opposite forces are added together, they completely cancel out.
Placing the wires near one another will decrease the amount of noise coming from those wires
because the magnetic fields will cancel.
The goal becomes, "How can we place these wires as close to the same position as possible?".
It's a similar goal to a coaxial cable where the two conductors share an axis.
Twisting wires is a less expensive way to get very close to achieving this goal.
If the wires are twisted, they will still not occupy the same exact position, but here's
what we accomplish.
The wires of our circuit will now alternate positions along the length of the cable.
This greatly reduces the possibility of cross-talk where the signal on one wire is induced onto
a nearby wire.
Not only does twisting wires help prevent the first problem with outgoing noise, it
also helps to address the second problem - incoming noise.
Remember that the signal on each of these wires of a circuit are opposite.
However, the signal induced onto these wires by a magnetic field will be identical in each
wire.
Twisting the wires makes sure that they occupy as close to the same position as possible
so that any of that magnetic noise around them will be as close to the same signal in
each and will result in as close to a complete cancellation as possible.
Let's see this in action.
I've created this experiment to help you visualize and hear the difference between a twisted
pair and an untwisted pair.
For this experiment, we'll use a signal generator which puts an equal but opposite polarity
signal on the red and the black wire.
We'll also use a tool that allows us to hear the magnetic noise created around each wire.
[BEEPING]
There are three sections of wires.
One section, they are completely separated.
The second section, they're a bit closer together.
And the third section, they're twisted.
What we'll hear is that the noise is most significant where they are separated.
It gets a little quieter where they're closer together.
And it almost completely disappears where they're twisted.
[BEEPING]
[LESS BEEPING]
Remember, there's a lot of electromagnetic noise all around us and so the static you
hear shouldn't be confused with the actual signal that we hear radiating from these wires.
I hope this video has been helpful.
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out the website at AudioUniversityOnline.com.
Thanks for watching and I'll see you in the next video.