ENGINEERING-43
Ohm’s Law → V = IR
Lab-01
Lab Data Sheet – ENGR-43 Lab-01
Lab Logistics
Experimenter:
Recorder:
Date:
Equipment Used (maker, model, and serial no. if available)
Directions
1. Note that in this and ALL OTHER Laboratory Exercises ENGINEERING UNITS must
accompany ALL Data-Entries and Calculated-Quantities
2. Ensure that the WorkBench has a Digital MultiMeter (DMM)
3. From the lead-rack, select a set of “banana Jack” lead wires; one BLACK and ONE RED.
These will serve as the input connection to the DMM
4. Go to the side counter collect a “bread board” and TWO “load” resistors, RL, required to
construct the circuit shown in Figure 1. Use the Resistor COLOR-CODE (see Appendix 1)
to select Load Resistors in these ranges:
 RL1= 500Ω - 1.4kΩ
 RL2= 1.5kΩ - 2.4 kΩ
The Ratio for RL2:RL1 should be  2:1
© Bruce Mayer, PE • Chabot College • 291211007 • Page 1
5. For the selected Load Resistors Record the COLOR-CODED Nominal-Resistance and
Resistor-Tolerance in Table I and Table II as in this Example:
RL,Coded =
Blue/Gray/Brown/Silver = 68x101 Ω ±10%
6. Use the DMM to Measure the ACTUAL value of the selected Load Resistors and Record
this value in Table I and Table II as in this Example:
RL,DMM =
729.6 Ω
7. Use various supply voltages to complete Table I and Table II for the Load Resistors. For
each Load Resistors Measure with the DMM1 the:
 potential across
 current thru it
8. Return all lab hardware to the “as-found” condition
9. Reduce the Data by completing the power calculations in Table I and Table II
10. For each load Resistor Use MATLAB or EXCEL to produce Cartesian (X-Y) plots For each
resistor use Vs as the INDEPENDENT, or “X”, Variable
 Vs v. IL
 Vs v. PL
 Where PL = (Vs,Actual)(IL)
 In other words use the MEASURED values of V & I to calculate P
 SQRT(PL) v. Vs
11. In the Space Below write a short comment on this Question
 How well do these carbon-resistors obey Ohm’s Law?
 HINT: Use MATLAB or EXCEL to perform Linear Regression Analysis on the
appropriate plot(s) produced for Direction Step-10.
1
CAREFULLY Select the DMM range such that meter displays at least THREE (3) digits, and FOUR digits if
possible. All DMM measurements should be reported to MAXIMUM POSSIBLE number of significant figures
© Bruce Mayer, PE • Chabot College • 291211007 • Page 2
Figure 1 • V = IR
Test Circuit.
RL = 1kΩ and 2kΩ
(nominally)
Raw Data and Calculations
Table I – V/I Measurements, Power Calculations – RL = 1 kΩ (nominal)
RL,Coded =
RL,DMM =
Vs,Nominal
(Volt)
Vs,DMM
IL,DMM
P = IV
(Calc)
P = I2R
(Calc)
1
2
3
4
5
6
7
8
9
10
© Bruce Mayer, PE • Chabot College • 291211007 • Page 3
P = V2/R
(Calc)
Table II – V/I Measurements, Power Calculations – RL = 2 kΩ (nominal)
RL,Coded =
RL,DMM =
Vs,Nominal
(Volt)
Vs,DMM
IL,DMM
P = IV
(Calc)
P = I2R
(Calc)
P = V2/R
(Calc)
1
2
3
4
5
6
7
8
9
10
Run Notes/Comments
Print Date/Time = 29-May-16/03:59
© Bruce Mayer, PE • Chabot College • 291211007 • Page 4
Appendix 1  Resistor Color Code
Introduction
Resistors are color coded for easy reading. Imagine how many blind technicians there would
be otherwise.
To determine the value of a given resistor look for the gold
or silver tolerance band and rotate the resistor as in the
photo at Right. (Tolerance band to the right). Look at the 1st
color band and determine its color. This maybe difficult on
small or oddly colored resistors. Now look at the chart and
match the "1st & 2nd color band" color to the "Digit it
represents". Write this number down
.
Now look at the 2nd color band and match that color to the same chart. Write this number next
to the 1st Digit.
© Bruce Mayer, PE • Chabot College • 291211007 • Page 5
The Last color band is the number you will multiply the result by. Match the 3rd color band with
the chart under multiplier. This is the number you will multiple the other 2 numbers by. Write it
next to the other 2 numbers with a multiplication sign before it. Example : 2 2 x 1,000.
To pull it all together now, simply multiply the first 2 numbers (1st number in the tens column
and 2nd in the ones column) by the Multiplier.
Example:




First color is red which is 2
Second color is black which is 0
third color is yellow which is 104 = 10,000
Tolerance is silver which is 10%
Therefore the equation is:
 2 0 x 10,000 = 200,000 Ohms = 200 kΩ
 Specified Range within which the actual resistance value must lie = [200 kΩ]•[±10%]
o = 180kΩ  Ractual  220 kΩ
The Code
Resistor Color Code Chart
1st. & 2nd Color Band Digit it Represents
Multiplier
BLACK
0
X1
BROWN
1
X10
RED
2
X100
ORANGE
3
X1,000 or 1K
YELLOW
4
X10,000 or 10K
GREEN
5
X100,000 or 100K
BLUE
6
VIOLET
7
Silver is divide by
100
GRAY
8
Gold is divide by 10
9
Tolerances
 Gold= 5%
 Silver=10%
 None=20%
WHITE
© Bruce Mayer, PE • Chabot College • 291211007 • Page 6
X1,000,000 or 1M
Tolerance
Resistors are never the exact value that the color codes indicate. Therefore, manufacturers
place a tolerance color band on the resistor to tell you just how accurate this resistor is made.
It is simply a measurement of the imperfections. Gold means the resistor is within 5% of being
dead-on accurate. Silver being within 10% and no color band being within 20%. To determine
the exact range that the resistor may be, take the value of the resistor and multiply it by 5, 10,
0r 20%. That is the number that the resistor may go either way.
Examples

A 1,000 Ohm resistor with a gold band maybe any value between 950 to 1050 Ohms.

A 22,000 Ohm resistor with a silver band maybe any value between 19,800 and 24,200
Ohms.
FAQ
Just a few common questions to help you out.
1. Which side of the resistor do I read from?
 The Gold or Silver band is always set to the right, and then you read from left to
right. Sometimes there will be no tolerance band -- Simply find the side that has a
band closest to a lead and make that the first band.
2. Sometimes the colors are hard to make out. How do I make certain what the value of
the resistor really is?
 Occasionally the colors are jumbled or burnt off. The only way to read it then is with
an OhmMeter or MultiMeter across the leads
3. How do I remember this sequence of colors?

Remember the color codes with this sentence: Big Brown Rabbits Often Yield Great
Big Vocal Groans When Gingerly Slapped.
Print Date/Time = 29-May-16/03:59
© Bruce Mayer, PE • Chabot College • 291211007 • Page 7