Hello, I'm Dr Ferri. In this lesson, we will do a Lab Demo for
an Introduction of Electrical Components. Specifically, look at basic instruments
and components that you use to build a real circuit.
Now, so far in this module, we've covered some, some more abstract ideas including
resistance Kirchhoff's Laws and resistors.
Now, we're going to look at real physical circuits.
So, the lab demo is on introduction of electrical components.
This experiment is to introduce you to some of the basic components of building
electrical circuits. This meter here is a multimeter, and it
has on there a way to measure resistance, DC voltage, AC voltage, DC current, and
AC current. Now, digital mutilmeters are very, very
common and you can get them very cheaply you know, less than $5 for a digital
multimeter. And you can use them around the house to
make sure you don't have broken electrical connections or that you've got
a wiring that's, that's doing, that's doing what it's supposed to do.
For example, if I want to see if I've got a electrical connection that's broken.
I would check the, the current or the resistance.
If I have zero resistance, that means I'll get a electrical connection.
So, for example, these two leads coming out.
Normally, I'd hook them up between two things I'm trying to find the resistance
between. If I just cross them, that means I've
short circuited these out. There's zero resistance between them and
I'm measuring zero resistance. And that's one way I usually check to see
if my multimeters got batteries in it. Because if I, if I cross the leads I can
tell I've got it's, it's working because I'm reading zero ohms.
Now, let's show a battery. This is a battery pack which measures
each of these batteries is one and a half volts.
And I put them in series with one another, so the total should be four and
a half volts. So, if I turn my multimeter to DC voltage
and I measure it, I get 4.35 volts. And actually, if I reverse this polarity
here, change the wires around, I would measure minus 4.343 5 volts.
So, it's pretty close to 4.5 and not exact because the batteries have a little
bit of leakage in them. And this is a protoboard.
A protoboard is really, really useful for building circuits.
It's because a lot of the electrical connections are made for you.
If I want to build a circuit, I can build components together, and I can cross the
wires. And it gets pretty messy if I have a lot
of crossed wires, because when I cross the wires I have to clamp them to make
sure they stay put. A protoboard board has the connections
made behind it. So for example, underneath every row of
five is connected together. So every row, every hole here is
connected to the other holes. And that's true of all these groupings of
five. So, if I look at this wire in here versus
a wire there. And I want to test the resistance, I get
zero ohms because they're connected together.
Similarly, along the side rails, all of these groups of ,of holes are connected
together. So this one and this one are connected
together. And if I test the resistance, I get down
to zero ohms. And similarly, this row is connected and
over here, this row is connected and this row is connected.
So, there's four groupings along the side.
So, every group of five up here is connected, but the ones are not connected
to each other. So this one and this one are in separate
rows. And if I check the it, it says open loop,
they're not connected. Now, the next thing I want to show you is
resistors. This is a common physical resistor, and
physical resistors come with color bands, so you are able to tell what resistance
they are. Now if you look up at the color code,
you'll see that these colors mean something.
The first two bands represent the first and second significant numbers.
And the colors are coded here from black, brown, red, orange, yellow, and so on.
So, this one, the first two bands are red and black.
That means that's a two and, and rather red and brown.
So, that's 2, 1. So, that's where we get a 2, 1.
And then the third band is orange, that means that there's three zeros after it.
So, it's 21,000 ohms. Now, the fourth band represents the
tolerance. Resistors are made pretty cheaply, so
there's, they're never exactly what they're supposed to be.
So, whenever they're made there's an, there's usually a little bit of tolerance
there. So, this one is marked as being a 21,000
ohm resistor. But the actual resistance, if you measure
it, is plus or minus 10%. There's also a, a gold band which
represents 5%. Now, going back to this resistor, the
first band is a brown and that represents the number one.
The second band is a black representing zero.
So I've got a 1, 0. And then, followed by the red band
meaning two more zeroes. So, I've got a 1, 0 and then 0, 0.
So it's a thousand ohms, plus or minus 5% because that's a gold, gold resistor.
Now, let's go ahead and measure it. So, this measures out at 989 ohms, which
is within the 5% tolerance because 5% of 1,000 is 50 ohms.
So, this is a 989 ohm resistor, even though it's marked at 1000 ohms.
So, in summary, the lab demo showed us examples of physical resistors, and we
introduced you to color codes to, to, to tell what the actual resistor values are.
And we notice that resistors, physical resistors are not exact and there are
tolerances on them. We introduce you to digital multimeters
and their use in measuring voltage, current, and resistance.
And we introduce you to a protoboard, often called a breadboard.
And it is used for ease of building circuits.
In the next lesson, we will do another lab demo.
And that's to introduce you to resistor connections and real circuits.