Magnetic Flux Cipher — Electromagnetism and Induction

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difficulty levels — click green to claim

> MAGNETIC FLUX CIPHER

flux difficulty: 2–5 field: electromagnetism

The idea in plain English: When electric current flows through a wire, it creates a magnetic field around it — the same principle that makes electromagnets work. The strength of the magnetic field depends on the current (more current → stronger field) and the distance from the wire (closer → stronger field). In this puzzle, sensors placed around wires measure the magnetic field strength at each position. Those field strength values, when converted to ASCII, spell the hidden message.

Why this really exists: Electromagnetism runs the modern world. Electric motors (used in EVs, fans, power tools) work by magnetic fields from current-carrying wires. Power generators do the reverse — spinning magnets induce current in wires. The Biot-Savart law describes this relationship, and engineers use it to design everything from MRI machines to wireless phone chargers.

▸ Concrete Example

A wire carrying 72A of current. Sensors at distance r = 1m:

B = μ₀ × I / (2π × r) (for a straight wire)
μ₀ = 4π × 10⁻⁷

B = (4π × 10⁻⁷ × 72) / (2π × 1)
B = 2 × 10⁻⁷ × 72
B = 1.44 × 10⁻⁵ T (tesla)

Scale to ASCII: B × 10⁷ = 144 → not valid ASCII?
The puzzle provides a scaling factor to map to valid character codes.

The magnetic field strength encodes the letter — the scaling factor is part of the puzzle data.

▸ How to Decode (Step by Step)

1. Get wire positions, currents, and sensor positions from puzzle data

2. Calculate the magnetic field at each sensor using Biot-Savart law

3. Apply the puzzle's scaling factor to map B to ASCII range (32-126)

4. Convert each scaled value to a character

5. Join → the answer word

def wire_b_field(current, distance):
return 1e-7 * 2 * current / distance

scaled = [int(round(b * scale)) for b in b_fields]
word = ''.join(chr(s) for s in scaled)

▸ Real-World Applications

Electric motors: EVs, fans, drills — all use magnetic fields from current
MRI machines: Huge magnetic fields (1.5-7T) create medical images
Wireless charging: Qi chargers use magnetic induction to charge phones
Transformers: Power grid transformers use magnetic flux to change voltage

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