Download Ohm`s Law Lab

Conceptual Physics Ohms Law Lab
To be done in your lab notebook
Remember, if at anytime you create a circuit that I have not assigned, you will receive a zero on
the assignment and not participate in any other labs until you’ve shown that you can do so safely.
Pre Lab:
 On a fresh piece of paper in your lab notebook write today’s date and the title of the lab.
 Don’t forget to continue the page numbers in your lab notebook.
 Don’t forget to add this lab and its page number to your Table of Contents.
1. Draw a circuit schematic that has an ammeter, one resistor, one switch and one generator.
Draw a voltmeter in parallel to the resistor.
2. In order for current to flow, what kind of circuit must you have? Why?
3. Define Ohm’s Law.
Procedure:
1. Glue in your Data Table underneath your pre-lab.
2. Turn the dial on your voltage source until it reads approximately 5 V on the scale on the voltage
source.
3. Plug a banana-banana lead to one terminal of your voltage source and put the other end in the
switch.
4. Connect the switch to your ammeter using a banana-banana lead.
5. Connect a banana-alligator to the other terminal of your voltage source and put the alligator clip
on one side of a resistor.
6. Take another alligator-banana lead and complete the circuit by connecting the other side of the
ammeter to the other end of the resistor.
7. In your Data Table, write down the value of the resistor as Resistor #1.
8. Using two additional banana-banana (or banana-alligator) leads, attach the Voltmeter in parallel
around the resistor. You only need to have a metal-to-metal connection in order for the
voltmeter to read the voltage so the leads can just be touched to the metal wires of the resistor.
9. To get the current to flow, close the switch.
10. Important! If the Ammeter or voltmeter tries to read below zero or into the negative, switch the
red and black plugs on your meter. It is trying to read a current or voltage going in the opposite
direction and just needs to be switched.
11. In your Data Table, write down the value of the current read off the ammeter as Current #1.
12. In your Data Table, write down the value of the voltage read off the voltmeter as Voltage #1.
13. Replace Resistor #1 with a second different resistor and measure the current again.
14. In your Data Table, write down the value of the resistor as Resistor #2.
15. In your Data Table, write down the value of the current read off the ammeter as Current #2.
16. In your Data Table, write down the value of the voltage read off the voltmeter as Voltage #2.
17. Replace Resistor #1 with a third different resistor and measure the current again.
18. In your Data Table, write down the value of the resistor as Resistor #3.
19. In your Data Table, write down the value of the current read off the ammeter as Current #3.
20. In your Data Table, write down the value of the voltage read off the voltmeter as Voltage #3.
21. Open the switch, disassemble the circuit.
Analyzing:
Underneath your circuit diagrams, write “Analyzing” and answer in complete sentences. Don’t
forget to number your answers!
4. How did Current #1, Current #2 and Current #3 compare to each other? Why were they
different?
5. Using the voltage from your voltmeter and the current from your ammeter, use Ohm’s Law
to calculate the theoretical Resistance #1 from your experiment. Show GUESS.
6. Using the voltage from your voltmeter and the current from your ammeter, use Ohm’s Law
to calculate the theoretical Resistance #2 from your experiment. Show GUESS.
7. Using the voltage from your voltmeter and the current from your ammeter, use Ohm’s Law
to calculate the theoretical Resistance #1 from your experiment. Show GUESS.
8. Compare your theoretical resistances from Applying Questions #5, 6, and 7 to the actual
resistance that is printed on the resistors that wrote in your data table. They will be slightly
different (which is normal); think of three reasons why the values could be different and
explain.
Applying:
Underneath your circuit diagrams, write “Applying” and answer these in complete sentences. Don’t
forget to number your answers!
In any factory where things are made there are some workers assigned to Quality Control to make sure
that the product that is put out is the best that it could be. Jen R. Aiter works in a factory that makes
electronic parts and is in charge of Quality Control for resistors.
9. Jen finds a resistor that is unlabeled. Explain how she could figure out the size of the resistor
so that she can label it correctly.
10. Jen tests another resistor and measures 100 mA running through it with a 3 V potential
difference across it. The resistor is labeled as 40 Ω. What is wrong with the resistor and how
do you know?