Today’s goal: Build simple circuits with battery-powered Christmas lights, then test and troubleshoot them.
You will:
Build a simple closed loop to light one section of lights.
Compare series vs. parallel setups.
Add a switch.
Use a step-by-step process to diagnose and fix circuit problems.
Success criteria: You can explain what makes a circuit work, identify common faults (open circuit, short), and justify your fix using evidence from testing.
Materials (per group):
Battery pack (with fresh batteries)
Battery-powered mini Christmas light string
Tape and/or foil (for quick connections)
Paperclip or clothespin (to make a switch)
Optional: alligator clip leads, spare bulbs (if your string uses replaceable bulbs)
Safety rules:
Battery power only (no wall outlets).
If the battery pack or wires feel warm/hot, disconnect immediately (possible short circuit).
Keep metal pieces (foil/paperclips) from touching both battery terminals at once.
What you’re trying to prove:
A circuit works only when there is a complete path from one battery terminal through the lights and back to the other terminal.
When it doesn’t work, you can find the fault by testing one part at a time.
Which situation describes a closed circuit?
Match each circuit word to what it means.
| Draggable item | arrow_right_alt | Corresponding Item |
|---|---|---|
Short circuit | arrow_right_alt | Provides electrical energy |
Wire/connection | arrow_right_alt | Uses energy; makes light |
Battery | arrow_right_alt | Path for current to travel |
Open circuit | arrow_right_alt | Opens/closes the circuit |
Load (lights) | arrow_right_alt | A break in the path |
Switch | arrow_right_alt | Current takes an unintended low-resistance path |
Turn the battery pack off (or remove one battery while you set up).
Find the two terminals where the light string connects to the battery pack.
Make sure each terminal has a solid connection (metal-to-metal contact).
Turn the battery pack on.
If the lights do not turn on, do only one change at a time:
Check battery orientation
Try new batteries
Tighten/retape connections
Checkpoint: Before changing anything else, be ready to explain where you think the circuit is open (broken).
A circuit must be closed for the lights to turn on.
You build two circuits using the same battery pack and identical mini bulbs. Which setup is more likely to keep other bulbs lit if one bulb stops working?
Goal: Make a circuit where current must pass through each bulb in one path.
Identify a single path for current: battery → bulb(s) → back to battery.
If your light string has sections, try lighting one section, then add another section in line.
Predict: If one bulb is removed/loose, what will happen to the rest?
Test your prediction safely:
If your bulbs are removable: gently loosen one bulb.
If not removable: carefully open one connection point (make a small gap).
Record: What changed, and what did you observe?
In a series circuit, what usually happens if one bulb is removed (or a connection opens) while the circuit is on?
A circuit must be closed for current to flow through the lights.
You connect two identical light sections to the same battery. Which setup will usually keep each section brighter?
Goal: Compare brightness and reliability.
Create one path so current must go through Section A and then Section B.
Turn the battery pack on.
Observe:
Are the lights dimmer than before?
What happens if one section is disconnected?
Record: Write one sentence describing what you observed in series.
In a series circuit, what usually happens if one bulb (or one section) stops working and creates an open circuit?
Goal: Compare brightness and what happens when one branch is disconnected.
Connect Section A and Section B so each one has its own path to the battery (two branches).
Turn the battery pack on.
Observe:
Are the sections brighter than your series setup?
What happens if you disconnect only Section A?
Record: Write one sentence describing what you observed in parallel.
Which statements about parallel circuits are true? (Select 2.)
Goal: Control the lights by opening/closing the circuit on purpose.
Turn the battery pack off.
Choose one connection point (a wire/foil/tape connection) to act as your "switch location."
Build a simple switch:
Paperclip switch: Tape a paperclip so it can touch (ON) or not touch (OFF) a metal contact.
Clothespin switch: Use the clothespin to pinch two metal strips together (ON) or apart (OFF).
Turn power on and test:
Does ON make a complete path?
Does OFF create a gap (open circuit)?
Checkpoint: Show your teacher your switch working at least 3 times (ON/OFF/ON).
When the lights don’t work, drag the steps into a good troubleshooting order: , then , then , then .
Check connections
Replace a bulb
Look for a short
Test one change
Check batteries
Troubleshooting scenario: The lights are off, and the battery pack feels warm. What is the safest next step?
Design a small "holiday display" using your lights that meets these constraints:
Uses only battery power
Includes a working switch
Includes at least two light sections
In your response:
Say whether your design is mostly series or parallel (or a mix).
Explain why you chose that setup.
Describe the first 3 troubleshooting checks you would do if it didn’t work.
Include one safety check you would do while testing.
(You can use words and/or a labeled sketch.)
Case 1: What is the most likely problem?
Case 1: Suggest one fix (1–3 words).
Case 2: Suggest one fix (1–3 words).
Case 1: Explain what you would test first and why.
Case 2: What is the most likely problem?
Case 2: What evidence makes you confident in your diagnosis?
Case 3: Safest immediate action (1–3 words).
Case 3: What is the most likely problem?
Case 3: Describe how you would find where the short is happening.