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Circuit Quest
Mission 31
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Circuit Quest
20 minmedium

MISSION 31 · BASIC ELECTRONICS

Find the Missing Road

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Troubleshooting uses a baseline, a testable explanation and one controlled repair. A circuit that has not lit yet gives evidence.

Public beta missionThese revised instructions are open for learning while actual-kit testing is pending. A grown-up must confirm every setup check before power is connected. If a rating, pin card or required check is missing, explore the idea on screen and leave the physical build unpowered.

Become the circuit detective

Your new skill: Troubleshooting uses a baseline, a testable explanation and one controlled repair. A circuit that has not lit yet gives evidence.

Revisit the skill you will reuse: Previous main-path missionPrevious main-path mission

Meet the parts

Match the names to your parts before you build. New parts appear when you first need them. You can point, say the name or show a grown-up.

Battery and holder

A battery supplies energy that can make a light glow or a motor turn. A holder keeps its connections in place.

Spot it and try it

Look for: Find the + and - marks and the matching holder or snap connector.

Before using it: Use only the supply named in this mission. Never join + straight to -; disconnect before rewiring.

Your turn: With power disconnected, trace the path from + through the parts and back to -.

Jumper wire and clip lead

A wire makes an electrical connection between two points. A clip lead grips a terminal.

Spot it and try it

Look for: Jumpers have small plug ends; clip leads have metal jaws. Colour helps us track a connection.

Before using it: Colour does not change a wire's job. Check both ends and keep bare metal away from other terminals.

Your turn: Follow one wire from start to finish and name what it joins.

Breadboard

This reusable building board joins some holes with hidden metal strips, so we can connect parts without soldering.

Spot it and try it

Look for: Find the centre gap, row numbers and power rails. The gap separates the two halves.

Before using it: Five holes in one numbered strip usually join; the strip across the gap does not. Some power rails have a break. Match your board diagram.

Your turn: Point to two holes on the same connected strip, then two that are separated by the gap.

Resistor

A resistor limits current in a path. Beside our LED it helps protect the light from too much current. Its resistance is measured in ohms.

Spot it and try it

Look for: Look for a small body with two legs and coloured bands; match its labelled value to the mission.

Before using it: Use the labelled 2.2 kΩ, 2.7 kΩ or 520 kΩ value specified. A resistor can face either way. Never replace LED current limiting with wire.

Your turn: Point to the resistor in the LED path. Explain why replacing it with a plain wire is not our test.

LED or light emitting diode

An LED turns electrical energy into light and works in one direction. We use it to show what a circuit is doing.

Spot it and try it

Look for: An untrimmed ordinary LED often has a longer anode leg and a shorter cathode leg. A flat rim often marks the cathode.

Before using it: Confirm polarity with the part card if legs are trimmed. Use the mission's resistor in series; never connect an LED straight across the battery.

Your turn: With power off, identify the two legs and point to its protective resistor.

WHAT YOU'LL USE

Match these to your kit

9V battery and snap connectorHalf-size breadboardOne ordinary LEDOne 2.2 kΩ resistorCompatible jumper wires

Gather from home

Adult or partner; paper clue record

Reuse kit parts between projects. Household materials are listed separately. Match every value, variant and rating before connecting power.

BEFORE YOU BUILD

Disconnect power before every change. Never join battery positive directly to negative. Keep the specified LED resistor in place. Keep metal out of mouths and away from mains sockets. Stop and ask an adult if any part becomes warm or smells unusual.

YOUR REWARD

+30 XPMission completion

PREDICT BEFORE YOU BEGIN

Predict the result before testing. You can say it, draw it or point. What evidence would change your prediction?

BEFORE YOU BUILD

Adult setup check: Standard kit check. If this check cannot be confirmed on your actual parts, read and explore the concept only; do not power the build.

YOUR CHALLENGE

Troubleshooting uses a baseline, a testable explanation and one controlled repair. A circuit that has not lit yet gives evidence.

NEW POWER-UP

Troubleshooting uses a baseline, a testable explanation and one controlled repair. A circuit that has not lit yet gives evidence.

Practise first: 1 and 5. Reuse the familiar circuit before changing one feature.

Adult help: Adult checks the first build and all exact part ratings; adult setup and supervision required for motor, foil and capacitor activities.

See the idea before you build

How a breadboard connects insideBreadboard connection groupsWithin one numbered row A to E are connected, and F to J are connected separately. The centre gap separates them. Adjacent numbered rows are separate. Rail breaks vary; check your supplied board.151617ABCDEFGHIJCentre gap: no internal connection across

Each coloured strip is one connected group. Different numbered rows stay separate. This explains the board; use the mission’s exact connection reference for component positions. Check rail breaks on your supplied board.

Read the detailed lesson

What to look for

The safe open connection is identified and the working circuit recovered twice.

Why it works

Troubleshooting uses a baseline, a testable explanation and one controlled repair. A circuit that has not lit yet gives evidence.

Check your explanation

Why repair one thing before testing again? It shows whether that repair explains the result.

Check the connection map

CONNECTION MAP

Build the electrical path before you test.

Keep power disconnected while changing connections.
JoinConnectWhy it matters
19V + → 2.2 kΩ → LED anode; LED cathode → 9V −.Follow the named electrical nodes and component values; power off while connecting.
Trace the complete protected output path before power.
Confirm the project-specific adult setup check.
No battery short circuit; no bare contacts touching unintended terminals.

BUILD PATH

STEP 1 OF 4

Prepare and predict

Try · Notice · ExplainRead the checkpoint, make a prediction, then test your idea.

Prove the baseline and disconnect. A partner removes only the designated return jumper and isolates its free end.

Find the Missing Road — step 1

A video demonstration will appear here when it is ready. You can follow the written step now.

Read the video instructions

Prove the baseline and disconnect. A partner removes only the designated return jumper and isolates its free end.

Need a diagram for this step?

WHAT'S REALLY HAPPENING?

Why it works

Troubleshooting uses a baseline, a testable explanation and one controlled repair. A circuit that has not lit yet gives evidence.

FAIR-TEST CHALLENGE

Change only the feature named in this project; keep the supply, parts and observation conditions the same. Repeat the comparison.

WHEN IT DOESN'T WORK YET

Debug one clue at a time.

The result differs from the prediction

Likely cause: An open path, wrong node, polarity mismatch or a part variant that needs review.

Try this first: If the baseline did not work, return to First Light before adding any fault.

Any part warms or smells unusual

Likely cause: The setup needs adult inspection.

Try this first: Disconnect immediately. Do not retry until the fault is identified.

CLEAN, RESET AND STORE

Switch off and disconnect all power. Let moving parts stop. For capacitor projects, discharge through the 2.2 kΩ resistor for ten seconds with battery disconnected. Return loose parts to the box.