Welcome back, this is Dr. Ferry.
This lesson will be on a lab demo, The Applications of Inductance.
So far in this module, we've talked about the theoretical aspects.
We've learned how to analyze circuits with capacitors, inductors.
And it's a nice way of ending out this module, is to look at some physical
applications of inductors and capacitors. We've already done a lab demo on
capacitors. So now this time, we'll be doing a lab
demo on the applications of inductors and inductance.
Now let's [INAUDIBLE] look at some applications of inductance.
An inductor is just basically a coil of wire.
Inductors are really common. And they're used in power generation,
inductive sensors, and in inductive actuators.
The basic mechanism to generate electricity is by moving a coil inside of
a magnetic field or by moving the magnetic field [INAUDIBLE] a coil.
A guitar pickup uses, the electric guitar pickup uses this sort of principle.
In that case, the electric guitar pickup has a permanent magnet, as shown here.
We've got a permanent magnet and a coil of wire wrapped around it.
And it generates a magnetic field because of that permanent magnet.
If I take I it in a conductor like a guitar, metal guitar string and I cross
through those lines, I'm going to generate current in this coil.
Now, let's take a look at a kind of a simple experiment to show a homemade
guitar pickup. This is a homemade guitar pickup.
It is just a bunch of wire coiled around, very fine gauge wire, coiled around a
permanent magnet. And it creates magnetic field about it.
And this is a metal guitar string. As I pluck it [SOUND] then it cuts those
magnetic lines and it creates a voltage. Now this line showing out here, this is
connected to oscilloscope. So the only electricity that's going on
here is the one that I'm generating. [SOUND].
There's no external power supply here. If I look at the oscilloscope, as I pluck
this [SOUND] you can see the generated voltage.
[SOUND]. And that's how guitar pickups work.
They're just sensors made of this induction, inductive element.
Now this is a passive sensor, looking back at this experiment here.
This is a passive sensor. As I said, there's no external power
supply. Active sensors, which have their own
power supply, are often used in metal detectors and in inductive proximity
sensors. Going back to this drawing here, they act
as sensors, have a current flowing through this because of the power supply.
So they've got current flowing through this.
And that generates this electric field or magnetic field.
And, in fact, if you have a changing voltage or, changing current through
here, it's going to have a changing magnetic field.
When that comes in contact with a metallic object, it interacts with this
field, which then changes the current flow in the coil.
And there's a circuitry attached to that that detects that change in the current.
A very common inductive sensor that you'll see in applications is metal
detectors. Metal detectors of the kind of portable
type that you can find metal on beaches, but also metal detectors that are in
stores and events when you have to walk through the metal detector to get in.
It's just a magnetic field that you're walking through, and the metal disrupts
that magnetic field which then, again, disrupts the current generating that
magnetic field. A very common inductive sensor in
mechanical systems is a linear variable differential transformer, an LVDT.
That's that's a case where I've got a primary coil and in addition, I'm going
to have a secondary coil. And this is used to measure linear
displacement in mechanical applications. Now, inductive actuators, are ones that
drive mechanical devices. They rely on the principle of
electromagnet, which is again a coil with a current flowing through it.
If I just have just the basic coil with a current flowing through it, it generates
a magnetic field. The stronger the current, the stronger
the magnetic field. And that means I've created a magnet, an
electromagnet. [SOUND] This is an example of
electromagnet. I've got two leads here.
I hook up these leads to a power supply and inside here is a coil of, of wire.
And this, when they, current going through that coil gets large enough, the
magnetic field gets large enough, it becomes a magnet.
A solenoid is a electromagnet which has a core that goes into it.
And that core is pulled in when the electromagnet, magnetic field gets large
enough. So when the current gets large enough,
magnetic field gets strong enough, it pulls this in.
Now this right here is just a mechanical spring.
And it's used to provide a restoring force because when the current gets low
enough then the magnetic field drops, but I need a restoring force to push it back
out. So the magnetic, the magnetic field pulls
it in. The spring pushes it back out.
[SOUND] Let's see the operation of a magnetic, of a solenoid.
Solenoids are often times used as valves to open and close valves.
Now this is one that I've got hooked up to a power supply and I'm going to turn
this. Let me hold my finger on it to, because
it's going to move. I'm increasing the voltage this and,
thereby, increasing the current. [SOUND] And this one I got to about 14,
15 volts. It reached half an amp, which is quite a
bit. And the half an amp, it's large enough, a
strong enough magnetic field, that it pulled that shaft inward.
If I drop the current, the [INAUDIBLE] voltage and current through this,
[BLANK_AUDIO] at some point in time the, the spring force is large enough to pull
it back out. So that is a solenoid, oftentimes used
as, to open and close valves. [SOUND] Another example of an
electromagnet is in a loudspeaker. This is a cross-sectional area of a
loudspeaker. It's cut in half.
And this is a coil that's in there. So the coil is also cut in half.
You can see the inside of the coil. So the coil of wire is right there.
You can see it, a full one looking right there.
And there's a diaphragm or cone attached to the electromagnet.
And the electromagnet reverses polarity depending on how you, what the current is
like going through these coils, through the coil.
It reverses polarity, pushing against or pulling the diaphragm towards a
[INAUDIBLE] permanent magnet. So as you reverse the polarity of the
current going through that, that, coil, it's going to push or pull this speaker
inward and outward, this diaphragm. And, therefore, it creates the sound.
So that's a good application of of inductance.
So we've looked at inductance with respect to sensors, as well as actuators.
In summary, we discussed the energy exchange in inductors, from mechanical
energy to electrical, and from electrical to mechanical energy.
And that was done all through inductors. We also shared that moving a conductor in
a magnetic field induces current. And changing current in a coiled wire
causes a magnetic field. And we use these properties to be able to
build applications with inductance. We looked at passive sensing, such as, in
a guitar pickup. We looked at active sensing, such as
metal detector. And we also looked at actuation through
the, the usage of solenoids with speakers.
I like to remind people to go to the forum and ask questions as you need,
answer questions that other people, post. And you might want to start a new forum
topic that is applications of inductors and capacitors that you're familiar with.
Thank you and I'll see you online.