Sankey Diagrams

Lab Brief #7

🎯 Your mission

Understand the idea. Then look for it everywhere.

⚡ The twist

Speed isn't the same as force. Don't mix them up.

What you'll learn

A Sankey diagram draws energy flow as arrows whose widths are proportional to the energy carried. Input enters from the left, useful output continues right, and wasted energy branches downwards. The widths must always add up.

Key words

Sankey diagram
A flow diagram whose arrow widths are proportional to energy transferred.
input energy
The total energy supplied to a device.

Make a hypothesis first

Guess: where does the energy go?

Say your guess out loud — then find out if you were right.

Step 1 of 4 · Read

Think about what you just learned: say what "Sankey diagram" and "input energy" mean in your own words before you start.

Step 2 of 4 · Do

Draw a scaled Sankey diagram for a filament lamp taking 100 J and delivering 5 J of light, then one for an LED lamp taking 100 J and delivering 40 J. Use 1 mm per joule and check both diagrams balance.

Step 3 of 4 · Observe

Record what actually happened, including anything that did not match what you expected.

Step 4 of 4 · Record

Write a conclusion that answers the question this lesson opened with, and state your uncertainty.

Question 1 of 2

In a Sankey diagram, arrow width represents:

How sure are you?😐 maybe

Question 2 of 2

A lamp takes 100 J and gives 5 J of light. The wasted energy shown is:

How sure are you?😐 maybe

Mind = blown

🔥 A bolt of lightning is 5 times hotter than the surface of the sun.

Nice work!

You got 0 of 2 right.

Next: Elastic Potential Energy All lessons

🎯

Next Smart Experiment

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✨ More to explore

🌍 Where you see this in real life: You use this every time you flip a light switch, ride a bike, or kick a ball.

🏆 Stretch challenge (try it this week): Time how long a small ball rolls down something, then change the slope and try again.

👨‍👩‍👧 For the dinner table: “Show me something at home that uses this kind of energy.”

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