PLC Activity #4
Series and Parallel Lightbulb Circuits
Due: see webpage for due date
How to get credit for this activity
First, sign-in at the computer and sign-out when the activity is complete. Show your work
and results to a PLC tutor so they can check your work and initial the signoff sheet. Be
prepared to answer questions about the activity or your results.
Mystery Circuits
There are three mystery circuits that consist of an unknown combination of series and
parallel connections. For each circuit, use your knowledge to determine how the different
lamps are connected. You should try the following experiments to aid in your
investigation:
 Remove one lamp from its socket and see how it affects the brightness of the
remaining lamps
 Use the voltmeter to measure the voltages across each lamp or across
combinations of lamps
 For each mystery circuit, discuss the results with your group members and then
draw your best guess for how the lamps are connected.
Mystery Circuit 1: (set power supply to 12 V)
Mystery Circuit 2: (set power supply to 6 V)
Mystery Circuit 3: (set power supply to 8 V)