Fundamentals/Power and protection

Every part in front of the board is there because something died.

A fuse that takes 150 milliseconds. A diode that charges you half a volt. A cell that vents at 4.3 V. Each one is a specific answer to a specific failure — and each has a chip that does the same job better.

A short circuit is the load going to nearly zero ohms. Two parts stand between that and your supply, and they are not remotely equally fast.

A battery fitted backwards, two supplies feeding each other, and a spike arriving down the cable. Three problems, and four parts that answer them.

The only part on the bench that stores enough energy to hurt you, and the four chips people put in front of it.