Physics 360 Neumann
Virtual Lab 4 – Electric Circuits PHET
Name(s): __________________________________________________________________________
Purpose
Finding voltages, currents, and power losses in an electric circuit; practicing with parallel and series connections.
For this lab, we will be using a Virtual Lab, available through PHeT. It can be found here:
https://phet.colorado.edu/en/simulation/circuit-construction-kit-dc-virtual-lab
We will be using three resistors (30 Ω, 60 Ω, and 120 Ω), two batteries (variable voltage), and some lightbulbs.
Part I: Resistors in Series and in Parallel
1. Calculate the equivalent resistance you would get if you connected all three resistors (values above) in series.
Show your work.
Series Req = ________________ [Ω] (show calculations)
2. Repeat the previous step for the case where all three are connected in parallel.
Parallel Req = ________________ [Ω] (show calculations)
PART II: Series circuit
3. We’ll call your three resistors R1, R2, and R3, respectively, in order of increasing resistance. Connect the three
resistors and one battery into a Series Circuit (see figure below).
4. Adjust the values of the resistances to the values listed above by clicking on each resistor.
5. Click on “Conventional current” button on the right, and notice the arrows representing the current. Play
around with the battery voltage, and describe what happens to the current.
6. After performing the previous step, adjust the voltage of the battery to 30.0 V.
7. Use the Voltmeter button on the right to measure and record the voltage across different elements indicated
in the above figure. Remember, to measure voltage, the voltmeter has to be connected ACROSS the resistor.
Be careful to observe the polarity of the leads (red is +, black is -).
8. What happens when you reverse the polarity of the leads? Why does this happen?
9. Discuss any trends regarding a pattern for how voltage gets distributed in a series circuit. Is there any
relationship between the size of the resistance and the value of the resulting voltage? Explain.
_____________________________________________________________________________________________
10. Use the ammeter to measure and record the current at the indicated points in the above figure. Remember
that in order to measure current, the ammeter has to be connected in SERIES, which means that the circuit has
to be disconnected and the ammeter inserted as part of a circuit.
11. Discuss any trends regarding a pattern for how current behaves in a series circuit.
PART III: Parallel circuit
12. Disconnect your series circuit and construct a
parallel circuit using all three resistors (see figure)
13. Use the voltmeter to measure and record the
voltages indicated in the figure.
14. Discuss any trends regarding a pattern for how
voltage gets distributed in a parallel circuit. Is there
any relationship between the size of the resistance
and the size of the resulting voltage? Explain.
15. Use the ammeter to measure and record the currents
indicated in the figure. Again, remember to connect
the ammeter in SERIES.
16. Discuss any trends regarding a pattern for how
behaves in a parallel circuit.
PART V: Combination circuit.
17. Disconnect your parallel circuit and connect the combination circuit shown below. Describe qualitatively what
happens with the red arrows representing conventional current, as this current flows through the different
resistors.
18. Before making any measurements, calculate the voltage across each resistor and the current through each
resistor, using the resistance values listed above (in increasing order). Show work!
19. Use the voltmeter and ammeter to measure and record the voltages and currents indicated in the figure, and
record all the values.
20. Replace the resistors with lightbulbs of same resistance values. Qualitatively compare brightness of the three
lightbulbs.
21. What were the two most important things you learned or reviewed during the course of this lab?
