Name: _________________________________HR:____
Ohm’s Law Lab
Introduction: (fill in the blanks!)
Ohm’s Law tells us the relationship between current, voltage, and resistance. Ohm’s Law tells us
____________________ is directly proportional to ________________ and inversely proportional to
_____________________. The triangle equation to show this is given below:
V
I
R
Objective
Your task is to calculate the resistance of three unknown resistors in a series circuit.
Materials



Ammeter
3 wires (1 red, 1 black, 1 yellow)
Voltmeter


Resistors (3 different)
DC Power Source
Procedure
1. Setup your materials as seen below. (Draw picture and take notes during pre-lab discussion!)
2.
3.
4.
5.
6.
7.
Pick up a resistor from your teacher and record which resister you have. Place the resistor in the circuit.
Turn on the power supply and adjust so the current is no greater than 0.2 amps!
Record the amount of current flowing in your system.
Using the multimeter (set on 20 V), measure the voltage across your resistor.
Use Ohm’s Law to calculate the resistance.
Repeat steps 3-6 with the same resistor but change the current flowing through it (still no more than 0.2
amps!). Make sure you record values for each trial!
8. Record the colors of the bands of each resistor in the data table. THIS IS IMPORTANT FOR LATER!
9. Repeat steps 3-8 for each resistor (total of 3)
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Data and Calculations (Don’t forget your units!)
Show your work below!
Resistor #_______
Trial 1
Trial 2
Trial 3
Current
Voltage
Resistance
Colors of Bands
(Gold is last)
Resistor #________
Trial 1
Trial 2
Trial 3
Current
Voltage
Resistance
Colors of Bands
(Gold is last)
Resistor # _________
Trial 1
Trial 2
Trial 3
Current
Voltage
Resistance
Colors of Bands
(Gold is last)
Calculate the average resistance of each resistor based on your data. (Don’t forget units!)
Resistor Number
Average Resistance
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Data Analysis
Use the information below to determine the actual resistance of each resistor you used based
on the color bands you observed. (Don’t forget units!)
Resistor Number
Actual Resistance
Read the colors from left to right.
The first band is the first number,
the second band is the second
number, the third band is the
multiplier band (number of zeros
to add to the two digit number),
and the fourth band is the
tolerance band. Tolerance
values for four band resistors can
only be 2%, 5%, or 10% (red,
gold, or silver respectively).
For example:
Brown = 1, Black = 0, Red =2
(two zeros must to added), and
Silver = ±10%.
1000 ohms or 1k ±10%
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Concluding Questions
1. On graph paper, create a graph of Voltage (y) vs. Current (x) for each resistor. Draw a line
of best fit for each resistor (there should be 3 lines).
2. What do the slopes of the lines on your graph represent?
3. Describe the relationship that you see between voltage and current?
4. How does this experiment demonstrate Ohm’s Law? Explain your answer in detail.
5. What are at least 2 errors may be present in this experiment? How could you avoid these
errors if you were to redo the experiment?
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