Quick trick to check if your alkaline batteries are dead (no voltmeter required!)

I work as a sound technician, and the other day, I had to replace the batteries in a wireless microphone. But someone had mixed old and new batteries, and I didn't have a voltmeter to check them.

My colleague gave me a simple trick: drop the battery on a table. If it bounces, it’s used (empty). If it stays mostly still, it’s full.