## Puzzle: A Cube Of Resistors, Updated With Links To Solutions

I posted this puzzle a few days ago: Consider 12 identical resistors connected to form a cube. That is, each resistor lies on the edge of a cube, and there is an electrical connection joining three resistors at each of the cube’s eight vertices. What is the effective resistance between two vertices across a body … Read more

## Puzzle: A Cube Of Resistors

Here’s a puzzle I just read in Clifford Stoll‘s book High Tech Heretic (paraphrased by me): Consider 12 identical resistors connected to form a cube. That is, each resistor lies on the edge of a cube, and there is an electrical connection joining three resistors at each of the cube’s eight vertices. What is the … Read more

## Why Does A Propane Torch Get Cold When Used? Updated, With Refrigerators

I was fixing a leaky water pipe in my garage yesterday, and so I had occasion to use a propane torch to heat up the pipe and melt the solder into the joint. It’s not something I do often, but I do remember learning from my father (who was experienced in plumbing, and was somewhat … Read more

## When a Metal Ring is Heated, Does the Hole Expand, Contract, or Stay the Same Size?

Spoiler alert: The puzzle is answered in the update at the end of this post. Most solids expand when heated and contract when cooled. Water/ice is anomalous in that it expands when cooled, at least near its freezing point. If you’ve been unfortunate to forget a bottle of water in the freezer, only to find … Read more