Theme 1: Franklin

Welcome to The Inventor's Workshop.

Over the next eleven sessions you'll rebuild two of the most important inventions in early American history — Franklin's electrical safety systems and Bushnell's submarine. You'll build them, break them, fix them, and push them further than the originals.

You'll work in pairs. Your 📓 Inventor's Notebook lives in this classroom all summer. It travels with you across every invention.

We start with Benjamin Franklin.

Theme 1 of 3

Benjamin Franklin — Electricity and Safety

Franklin didn't just discover that lightning was electricity. He invented the first system that could protect people from it — the lightning rod. He drew the first diagrams of how electricity flows. He invented words you still use: battery, conductor, positive, negative, charge.

This week you'll build with electricity, design a lightning rod, and create an alarm system that warns when something goes wrong. Four sessions. One toolkit you'll use the rest of the summer: circuits, conductivity, and the Makey Makey.

⚡ Spark

Today you'll wire a real electrical circuit — battery, resistor, LED — then use a Makey Makey to hunt for which everyday objects conduct electricity. The answer's more surprising than you'd think.

History spotlight

In 1752, Franklin flew a kite into a thunderstorm. A wet kite string carried electricity down to a metal key tied near his hand — proving lightning was the same stuff as the static shocks from a doorknob. Until then, nobody knew. He nearly died doing it. Two other scientists trying the same experiment that year did.

Instructions
Part I: Build the circuit
Materials at your table
  • 1 nine-volt battery with snap connector
  • 2 alligator clip leads
  • 1 LED
  • 1 resistor (220Ω — small striped cylinder)
  • Optional: 1 piezo buzzer (try it in place of, or alongside, the LED)
  • Tape

The 9V battery puts out enough voltage to instantly fry an LED if you wire them together directly. So engineers add a resistor — a small component that limits how much current can flow through a circuit. With it in line, the LED runs all day. Without it, two seconds and it's dead.

  1. Snap the connector onto your 9V battery. You'll see a red wire (+) and a black wire (−).
  2. Look at your LED. One leg is longer than the other. The long leg is positive (+).
  3. Use one alligator clip to connect the red wire to one end of the resistor. Direction doesn't matter for the resistor itself.
  4. Use the second alligator clip to connect the other end of the resistor to the long leg of the LED.
  5. Touch the short leg of the LED to the black wire. The LED should light.
  6. Tape it in place. You just built a circuit — a complete loop where current can flow.
If it doesn't light: Flip the LED — the long leg has to face +. Or check that the resistor is actually in the loop, not just lying near it. Or try a different LED (they break sometimes — that's why your table has spares).

Want a different output? Swap the LED for the piezo buzzer. Same wiring — through the resistor, into the buzzer, back to the battery. Listen for the buzz. Want both? Wire them in line. Get creative.

In your 📓 Inventor's Notebook, sketch your lit circuit. Label every component: battery (+/−), resistor, LED (or buzzer), and the direction of current flow.
Instructions
Part II: Meet the Makey Makey

Your Makey Makey is a small green board that lets you turn any object that conducts electricity into a key on the keyboard. A banana can be the spacebar. A spoon can be an arrow key. Anything conductive.

Setup — once per pair
  1. Plug the Makey Makey into your laptop with the USB cable. It will recognize itself as a keyboard.
  2. Open a blank Google Doc.
  3. Clip one alligator clip to the spot on the board marked SPACE. Clip another to EARTH.
  4. Hold the EARTH clip in one hand. With your other hand, touch the SPACE clip. A space should appear in your doc.
Not working? Make sure both clips are touching metal on the board (the holes, not the plastic). Make sure your hand is on EARTH the whole time. If still nothing, ask another pair — they'll probably spot it in 10 seconds.
Instructions
Part III: Conductivity hunt

Take your free alligator clip (the one not held in your hand) and touch it to an object instead of your finger. If the object conducts electricity, a space appears in the doc. If it doesn't, nothing happens.

Hunt the room. Try at least 10 things.

Try these — predict before each:

A banana · a pencil tip (the graphite, not the wood) · a coin · the door handle · a piece of paper · a leaf · a desk · a person · a glass of water · your shoelace · a paper clip · a rubber band

In your 📓 Inventor's Notebook, fill in the conductivity table. Predict first, then test. Note anything that surprised you.
Discuss with your pair before you leave:
  • What's the common feature of things that conduct?
  • Did anything surprise you? (Most kids are surprised by at least one item.)
⚡ Strike

Yesterday you proved electricity needs a complete path. Today you'll use that fact to do something Franklin actually did: save a building from lightning.

History spotlight

Before Franklin's lightning rod (1752), tall buildings burned down constantly. Church steeples were the tallest things in town and got hit first. Bells would be rung during storms to "scare off the lightning" — bell ringers were the most likely person in town to be killed in a thunderstorm.

Franklin's idea: don't try to stop the lightning. Give it a path. A metal rod higher than the building, with a wire running down to the ground. Lightning takes the easiest route, the rod is the easiest route, the building stays safe.

Instructions
Part I: Design the path
Your mission: Build a model house with a lightning rod that protects it. The rod has to be taller than the house. A wire must run from the rod all the way down to the "ground." When you simulate a strike, electricity should travel through the rod and wire — not through the house.
Materials at your table
  • Cardboard for the house
  • A wooden skewer or craft stick for the rod tip
  • Aluminum foil (the rod cap and the wire)
  • Tape
  • Your circuit from last session (9V battery + resistor + LED, still working)
  • 2 extra alligator clip leads

In your 📓 Inventor's Notebook, sketch your design before you build. Mark where lightning enters (the rod tip) and where it goes (the ground). The path should be the easiest one in the whole structure.

Instructions
Part II: Build
  1. Build a simple house shape with cardboard. It only needs to stand on its own.
  2. Tape your skewer or stick to the top of the house. Wrap foil around the top inch — this is your rod cap (the part lightning hits).
  3. Run a strip of foil from the rod cap, down the side of the house, all the way to the table or floor. The strip cannot be broken — it must be one continuous path.
  4. Insert your LED circuit into the foil path somewhere along the wire — when electricity flows, the LED lights up. That's your proof that the path works.
Instructions
Part III: Test the strike

Use one alligator clip from the battery's + side. Touch it to the rod cap. Use the other clip on the − side and touch the foil "ground" at the bottom.

The LED should light. That means the path works — electricity traveled all the way through your lightning rod from top to bottom.

If it doesn't light: Find where the path is broken. Run your finger down the foil — is there a tear? Is the LED installed the right way around? Is the foil actually touching the rod cap?

Now break it on purpose. Cut a small gap in the foil partway down. Test again. The LED should stop lighting. That's what happens to a real lightning rod when the wire breaks.

In your 📓 Inventor's Notebook, draw your tested system. Mark where the path could break. Write what you'd check first if the LED stopped lighting.
⚡ Defend

The lightning rod protects against something falling from above. Today you'll build something Franklin would have loved: a system that detects when something bad happens and tells the world about it.

You're building an alarm.

History spotlight

Franklin's most famous electrical "show" wasn't the kite — it was an electric bell system he wired up in his own house. He attached his lightning rod to a bell inside. When a thunderstorm rolled in and the rod started picking up charge, the bell would ring — telling Franklin a storm was getting close. The first electrical warning system. 1753.

Instructions
Part I: Pick your alarm
Your mission: Build an alarm that uses your Makey Makey to fire a Scratch sound or animation when a specific physical condition is met. You pick the condition.

Pick one scenario to build:

🚪 Door Alarm — fires when a door (or any flap) opens. Two pieces of foil on the door and frame touch when closed. When the door opens, the connection breaks — and your alarm fires.
💧 Water Alarm — fires when water touches the sensor. Two foil strips with a small gap. Water bridges the gap — alarm fires. Real-world: basement flood detectors.
👣 Pressure Pad — fires when someone steps on (or sets something on) a pad. Two pieces of foil with a paper spacer between. Weight presses them together — alarm fires. Real-world: medical bed sensors, doorstep alerts.
Instructions
Part II: Set up Scratch + Makey Makey

Open Scratch (scratch.mit.edu — no login needed). Start a new project and build this simple alarm:

  1. Drag a "when space key pressed" block onto the workspace.
  2. Under that, attach a "play sound" block. Pick a loud one — "Alert" or "Siren" work well.
  3. Under that, attach a "say HELP! for 2 seconds" block (or your own warning message).
  4. Test it: press the spacebar on your keyboard. Sound plays, message appears.
  5. Now plug in your Makey Makey. Press SPACE on the board — the same thing should happen.

Now wire your alarm sensor to the SPACE port and EARTH port on the Makey Makey. When the sensor triggers, your alarm fires.

Stuck on Scratch? Find another pair that's got theirs working. They'll explain it faster than the teacher can.
Instructions
Part III: Test for honesty — 10 trials

An alarm has one job: tell the truth. If it fires when nothing's wrong, people stop trusting it. If it doesn't fire when something is wrong, people get hurt.

Run your alarm 10 times. Count two things:

In your 📓 Inventor's Notebook, record:
  • True hits (alarm fires when condition happens): __ / 10
  • False alarms (alarm fires when nothing happened): __ / 10
  • Missed alarms (condition happened, alarm didn't fire): __ / 10

A truly honest alarm hits 10/10, with zero false alarms and zero misses. If yours doesn't — find why and fix it before the end of class.

⚡ Extend & Show

End of Franklin. You've built three things: a circuit, a lightning rod, and an alarm. Today you pick one to push further — and then you show the room what you made.

Instructions
Part I: Pick your extension

Choose one of these. You have about 45 minutes to build.

🔁 Combine them — wire your lightning rod to your alarm. When the rod takes a "hit" (touch + and − to the rod), the alarm fires. This is exactly what Franklin built in 1753.
🏠 Upgrade the rod — add a second house next to yours that doesn't have a rod. Show what happens to each when lightning strikes.
🚨 Upgrade the alarm — make Scratch do something more interesting. Flash colors. Play a custom message. Send three different alerts for three different sensors. Get fancy.
🆕 Invent something new — your own electrical safety system. Anything Franklin would have liked. Run it past the teacher first.
Instructions
Part II: Build and test

Build it. Test it. If it doesn't work, fix it. If it works, make it work better.

In your 📓 Inventor's Notebook, sketch the final version. Note one thing you changed during testing — and why.
Instructions
Part III: Mini-showcase — 90 seconds per pair

Stand up. Bring your build. Show the room.

When it's your turn, answer these three:
  1. What does it do?
  2. What went wrong the first time you tested it?
  3. What would you change if you had another day?

Listen while other pairs share. In your notebook, write down one idea from another pair you'd steal for next time.

That's Franklin. Circuits, conductivity, grounding, alarms. Everything you built this week becomes a tool you'll use next week.

Next theme, you meet David Bushnell — the man who built America's first submarine, in 1775, with hand tools, to try to win the Revolutionary War. Bring your brain. Bring your notebook. The Makey Makey comes along too.

Career Connection

Everything you did this week is real work. Electrical engineers design circuits, power systems, and safety controls — every phone, every car, every hospital monitor runs on their work. Lineworkers repair grounding systems on power lines (the same idea as your lightning rod, scaled up to thousands of volts). Fire alarm technicians and security system installers build the same kind of sensor-to-alarm setups you made today, just with bigger sensors and louder alarms.

Many of these jobs don't require a 4-year degree — community college or trade school programs get you working in 18 months to 2 years. The skills start with what you did this week: complete the circuit, ground the path, test for honesty.

Inventors Notebook and Teacher Support Documents

Back to Workshop
Next Lesson