Download Activity Section 1.3 ResistorLEDAndWebsites042714

Math 63
Resistor Activity
Name: _______________________________
Here are some web sites that offer great explanations of what resistors are and how they are used.
1) http://www.youtube.com/watch?feature=player_embedded&v=VPVoY1QROMg
When I viewed this video for the first time, I thought it was
kind of geeky and boring, until I got to the cool little
experiment at the end on homemade resistors. I now really
like this geeky looking guy and think the site is terrific. Click
on the link or do a search for MAKE presents: The Resistor.
2) http://www.doctronics.co.uk/resistor.htm
Lots of really good information here, easy
to understand, and it includes some cool
links including a color code converter
(which is a really nice way to check your
“color code math”).
3) http://www.youtube.com/watch?v=TZYlPQU9B4M
This site is not as exciting as others, but it does
show how to use the multimeter. It also has a short
demo on lighting up an LED and then showing the
effects of using a resister.
4) http://www.the12volt.com/resistors/resistors.asp
This site includes a color code calculator!
This is great for practicing how to use the
color code chart and checking your answers –
I used this one a LOT!
5) http://www.allaboutcircuits.com/worksheets/resistor.html
This website was one of if not the
best. You could spend hours here. It
includes worksheets and ALL levels of
detail about electronics. I HIGHLY
recommend this. You could spend
days/weeks on this.
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6) http://www.article19.com/shockwave/oz.htm
I liked this website because it was
interactive. It would be great for the
student who already has some
knowledge of electronics or for the
student who has the initiative to
learn new things using interactive
websites.
7) http://www.youtube.com/watch?v=bF3OyQ3HwfU
This is a nice little video on how to do
the basics on a multimeter. I wish I
had watched it before I got going. It
is definitely worth 4 minutes and 36
seconds of your time.
PART 1
Before we start the “hands on” part of the activity, let’s review some basic information.
A resistor is one of the basic types of electronic
components. Resistors have two terminals and a
semiconductor, such as carbon, in the middle. A
semiconductor is just what it sounds like:
something that conducts electricity but not that
well. While conductors like copper and gold are
used in circuits to let electricity flow freely, a
semiconductor is used to provide some
resistance to the flow of electricity. That is why
a resistor has that name.
http://www.circuitstoday.com/working-of-resistors
http://speakerbug.com.au/s
hop/index.php?main_page=i
ndex&cPath=16_5
http://mfpowerresistor.com/rr_
pw.htm
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When electricity flows through the semiconductor, some of it is turned into heat. The
higher the voltage, the higher the energy is. In most circuits, this heat is just wasted
energy that is cast aside or is blown away with a fan. In some devices, however, the
heat produced by the resistor is the main purpose of the circuit.
Electric stoves, for example, use large resistors to produce a lot of
heat to cook your food.
Electricity is measured in voltage (V) and amperage (A). The
voltage can be thought of as the pressure of the electricity, and the amperage as the
amount of electricity flowing through the circuit. Voltage, amperage and resistance are
related by the equation V = IR (voltage equals amperage times resistance). At a set
voltage, amperage gets lower as the resistance gets higher.
If you think of a circuit as pipe carrying water, it's easy to understand why resistance
lowers the amperage. If you put in narrower pipes without changing the water pressure
(voltage), it will decrease how much water can flow through the pipe at one amperage.
The information above was taken from http://www.ehow.com/how-does_4597224_a-resistorwork.html
Three more things to keep in mind:
1)
Ohm’s Law says: Voltage (volts) = Current (amps) * Resistance (ohms)
2)
If the voltage goes UP and the resistance stays the SAME, the
current must go UP.
3)
If the voltage goes DOWN and the
resistance stays the SAME, the current must go
DOWN.
V=I*R
Increase
V=I*R
Decrease
Our activity is going to begin with a homemade resistor.
Materials you need
1. Multimeter with 2 connectors, one going to the negative/black port in the meter (it should say
COM) and one going to positive/red port in the meter (it should have an ohms symbol  ).
2. Paper
3. Pencil (preferably #2)
We should have plenty of meters so you each can work with one. I want you to work together. That
means you help each other, but every person does their own thing. Each of you will turn in your own
paperwork. Make sure EVERYTHING in the packet is filled in.
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STEP 1:
Watch the video with the geeky guy.
http://www.youtube.com/watch?feature=player_embedded&v=VPVoY1QROMg
We will follow the same instructions shown in the video by doing the following:
STEP 2:
In the space below, using your #2 pencil, draw a bar 3 inches long and about ¼ inch wide (mark it at ½ in,
1 in, 2 in, and 3 in. Fill it in with your pencil and make it as dark and shiny as possible.
STEP 3:
Take measurements of your homemade resistor as shown in the video
by sliding one probe back and forth along the bar while keeping the
other in place. See how your results compare to other students. Pay
close attention to the units.
Be mindful of the units on the meter.
Units on the multimeter may or may not be shown on the readout;
they may be indicated by the dial setting.
Record the multimeter
reading at 3 inches
(the connectors are
furthest apart).
RECORD YOUR RESULTS IN THIS TABLE
Record the multimeter
Record the multimeter
reading at the
reading at the 1 inch
2 inch mark
mark.
(2nd furthest apart).
Record the multimeter
reading at the ½ inch
mark.
PART 2
Now, you will conduct the resistor test with an LED.
Materials you need
Your homemade resistor from PART 1
2 LEDs (I suggest different colors)
1 9-volt battery
2 connectors (alligator clips or the pinchers type - don’t pick 2 of the same color)
Pencil
You will not be using the multimeter!
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Select one of the connectors and clamp one end to the
positive terminal of the 9 volt battery. Clamp the
other end to the positive side of the LED.
The Positive (+)
side of the
battery is the
male terminal.
The Negative (-)
side is the
female terminal.
The positive side of
the LED is USUALLY
the one with the
longer leg.
The negative side of
the LED is the side that
has a flat edge. It can
be hard to see, so you
have to look carefully.
As shown in the video, you
may want to loop the LED leads so it doesn’t twirl in the
clamp. You may also want to loop the negative side of
the LED so it can rest on the “homemade resistor” more
easily.
Now, take the 2nd connector and clamp one end to the negative terminal of the battery and lay the other
end on the homemade resistor.
Slide the connector along your homemade resistor while the LED wire
is resting on the bar. Having the lights off will help you see if the LED is
lighting up or not. If the LED does not light, you may have the positive
and connections backwards. It must be positive to positive and
negative to negative. TRY NOT TO TOUCH THE LED WIRE TO THE
connector – IT MAY BURN UP/OUT.
Record your findings and observations.
1) What color resistors (LEDs) did you use?
2) Were the results different? If so, how were they different? Explain in detail.
3) Did you burn up any? If so, explain in detail what happened.
4) Provide comments on this part of the activity. What would you change? What worked? What didn’t
work?
5) Before this activity, how well did you understand resistors? How did you learn about them and what
was the application.
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PART 3
Now that you know understand what resistors do, you
will practice determining their values.
As shown previously, resistors come in many different shapes and sizes.
We are going to concentrate on the type depicted in the image on the upper right. Notice the
colored bands. Sometimes the color is duplicated and sometimes not. Each band color in a
specific location represents a certain value. By reading and combining all of the bands, we can
determine the value of the resistor. Resistors are measured in ohms named after the German
physicist Georg Simon Ohm. The symbol that represents ohms is the Greek letter omega (  ).
When resistors are manufactured, they are done so with certain applications in mind.
Therefore, the manufacturer makes the resistor to meet specific values. Living in a real world
means making a resistor EXACTLY the same value as designed is likely NOT to happen. So the
manufacturer/designer allows a variance or tolerance. That means they can go over or under
the design value by a certain amount. This variance is given in the form of plus/minus a
percent.
Example: A manufacturer is asked to make resistors with a design value of 480kΩ and a
variance (or tolerance) of 5%. This means, as shown in the table below, that the lowest value
acceptable is 456kΩ and the highest value acceptable is 504kΩ.
Design
Value
480kΩ
Variance
±5% 𝑤ℎ𝑖𝑐ℎ 𝑚𝑒𝑎𝑛𝑠 ± 0.05 ∙ 480𝑘Ω = ±24𝑘Ω
Acceptable Range
Low
High
480𝑘Ω − 24𝑘Ω 480𝑘Ω + 24𝑘Ω
= 456𝑘Ω
= 504𝑘Ω
Before reading the bands on resistors, you need to be familiar with numerical prefixes often
used. These are shown in the following table. We will only be using a few of these prefixes in
this activity.
Table of Common Metric Prefixes
Metric Prefix
Symbol
Power of
Factor
10
Using this table of prefixes,
Tera
T
1012
1,000,000,000,000
9
33M  33 mega ohms
Giga
G
10
1,000,000,000
6
6
Mega
M
10
1,000,000
=33 10 ohms
3
kilo
k
10
1,000
=33 1, 000, 000 ohms
-3
milli
m
10
.001
=33, 000, 000 ohms
-6
micro
μ
10
.000001
-9
nano
n
10
.000000001
-12
pico
p
10
.000000000001
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This color code chart on the right is what we will be following to “read and interpret” the bands
on the resistors. A color copy of this chart will be provided for your use as part of the activity.
Example: Inspect the resistor
shown on the right. The bands
(from left to right) are orange,
white, yellow and silver. The color
code table was used to determine
the design value of the resistor.
This is shown in the table below.
Resistor
Number
st
1 Band
Orange
Example
Color On Bands
3rd Band
2nd Band
Multiplier
White
4th Band
Tolerance
Yellow
Silver
Range
Design
Value
(DV)
Low
High
390 0.10*390
=351kΩ
390 +
0.10*390
=429kΩ
Yes,
because
3.6% is
within
±10%
Value Of Each Band
3
9
104
±10%
Measured Value From Multimeter
(MV)
376KΩ
% Error of MV = (DV – MV)/DV
(ignore the sign of your answer)*
(390-376)/390 = 3.6%
390,000=
390kΩ
Does the % Error of the
Measured Value Fall
Within the Allowed
Tolerance? Yes or No
*To get the percent of error, subtract the multimeter value from the design value. Divide that
answer by the design value. Ignore the sign of the answer. You will get a decimal. Change that
to a percent, then compare it to the +/- tolerance.
Select two different resistors (they should have different sequences of color) and fill in the
tables below. You will first determine the value of each resistor based on the colors and then
actually measure each resistor on the multimeter. Then compare how the design value
compares to the measured. If the resistor you choose has 5 values you can ignore the extra
band; we will be working with only 4 bands. Remember, the last band you are reading should
be either silver or gold.
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Resistor
Number
1st Band
1
Color On Bands
3rd Band
2nd Band
Multiplier
4th Band
Tolerance
2
Design
Value
(DV)
Low
High
Value Of Each Band
Measured Value From Multimeter
(MV)
% Error of MV = (DV – MV)/DV
(ignore the sign of your answer)
Resistor
Number
Range
st
1 Band
Color On Bands
3rd Band
2nd Band
Multiplier
Does the % Error of the
Measured Value Fall
Within the Allowed
Tolerance? Yes or No
4th Band
Tolerance
Range
Design
Value
(DV)
Low
High
Value Of Each Band
Measured Value From Multimeter
(MV)
% Error of MV = (DV – MV)/DV
(ignore the sign of your answer)
Does the % Error of the
Measured Value Fall
Within the Allowed
Tolerance? Yes or No
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COMMENTS ON PART 3 Give two observations or findings you made about the resistors you calculated and then measured. (EXAMPLE:
Were you able to get measurements? Did any of them fall outside the design range? Were the measurements
difficult to determine? What settings did you use on the multimeter? Did you have to change the settings
when going from one resistor to another? Did you choose the settings and then measure or measure and then
adjust the settings? Were the resistors difficult to read? Why? Were the resistors difficult to calculate? Why?
Give two positive comments about this activity.
Give two suggested changes to this activity to make it better.
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