This course explains how to analyze circuits that have direct current (DC) current or voltage sources. A DC source is one that is constant. Circuits with resistors, capacitors, and inductors are covered, both analytically and experimentally. Some practical applications in sensors are demonstrated.
3.1 Lab Demo: Electrical Components
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来自 Georgia Institute of Technology 的课程
Linear Circuits 1: DC Analysis
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从本节课中
Module 3
This module demonstrates physical resistive circuits and introduces several systematic ways to solve circuit problems.
与讲师见面
Dr. Bonnie H. FerriProfessor
Electrical and Computer Engineering
Dr. Joyelle HarrisDirector of the Engineering for Social Innovation Center
School of Electrical and Computer Engineering
Dr Mary Ann Weitnauer
[SOUND] Welcome back to Linear Circuits.
This is Doctor Ferri.
In this lesson,
we're going to do a lab demo to introduce you to electrical components.
And the objective is to show you how to use real components and instruments.
This is the first instrument we're going to look at.
It's a digital multimeter.
Very very useful around the house.
I use it all the time to check things like voltages.
You can get these at the store for say as little as five dollars, or
they can cost several hundred dollars for really good ones.
So for example if I want to test voltage levels.
I would take the dial, put it over to the voltage, and I got it on a 20 range.
So let me take a battery pack right here.
These are double A batteries and I've got three of them in series.
Each one is one and a half volts, so the total should be 4.5 volts.
So I'm going to turn it over and measure across here.
So I've got -4.75.
And that's within range.
If I change the polarity and just switch these now, I've got 4.75 plus voltage
Now another thing that I use this for is to check connections.
And I'm going to change this over to the resistance,
you see the ohm sign right there, that's for resistance.
So if I want to see if I've got electrical connection,
I just check to see if I have zero resistance.
So in this particular case, if I'm going to cross these wires,
I have shorted this out and I have, it's showing zero ohms.
And that's actually one way I want to make sure if I've got power
to this if my batteries in my DMM are okay.
I always check to make sure that when I cross these I should get zero resistance.
Now let’s at look a real resistors.
What I want you to see is that there are color bands on here.
And we use those color bands to be able to tell the voltage or
the value of these resistors.
Now let’s look at a color code.
Now these particular resistors
that I'm using are gold-banded, and they also come in silver-banded.
And that corresponds to the tolerance, because resistors are not ideal,
there's going to be some variation in their values.
These particular ones,
these silver and the gold-banded ones have four bands to them.
The first two bands are the significance numbers and
the third band is a multiplier or we can also say the number of zeros.
And then the fourth band is the tolerance.
There are ten color codes here.
And they are shown here.
So this particular examples with the red, brown, orange,
silver, corresponds to the red, and the brown corresponds to a two and one.
And then the orange corresponds to three zeroes afterwards.
So this is a 21,000 ohm resistor or 21k with the silver band meaning 10%.
Now I should note that there is an other type of common resistor tolerance and
that's 1%, and 1% we would have five bands instead of four bands.
This resistor here is a brown, black, red, and gold.
So brown, black would be 1 0.
Red would be 2 0 afterwards.
So this is a 1K resistor.
Let me go ahead and measure it.
And if I look at the values there,
it's reading 0.985 and it's on a 2k scale right here.
So that means we're on a kilohm scale and that is corresponds to
0.987 kilohms.
Now the other one, this has a two in front, it has the red,
this should be a 2k, so if I measure it.
It's coming out to close to 2k, 1.977.
So both of them are within the 5% tolerance.
Another component that we want to talk about is a breadboard.
A breadboard is used to help us build circuits pretty easily.
The reason it's useful is because it makes a lot of connections for you.
Every grouping of five along here is connected to the other.
And along here, these long connections,
we oftentimes call them the rails, they're all connected together.
So for example, if I put a wire here and in the same row another wire.
And then I want to test that connection,
then I can check the resistance here.
And what we're seeing is zero resistance.
So yeah, it's in the same row.
These are connected electrically together.
And the same way if I did this up here.
Anywhere along the top, I check the resistance, and
it shows that they are connected together.
When I'd like to put a resistor into this breadboard.
I want to put it across rows.
I don't want to that put both ends in the same rows because otherwise I would be
shorting it out.
And then if I want to check resistance while it's in here,
then what I tend to do is hold these leads at the base of it like that.
Just so that I get a nice connection that shows metal to metal.
So here, I'm checking the 1K resistor, and again, we get .98 ohms.
In summary, we've gone over some basic concepts here.
The first one is the idea of resistors,
the fact that they're color coded and they all have meanings.
There's these bands on there and
then there's meanings for the value of them as well as the tolerance.
We've also looked at a digital multimeter or
DMM to measure voltage, current, and resistance.
And finally, we looked at breadboards, which we also often called protoboards,
because protoboards is just a way of prototyping a circuit.
And just as a reminder there, all of the rows are connected together,
so these grouping of five is one node, they're connected electrically.
And along the top, everything in one row cross here is connected, so
these are as if it's one node across the top.
All right. Thank you.
[SOUND]
