Notes:
Remind students that short-circuit testing of electrical power sources can be dangerous. A student of mine once stuffed a 6-volt "lantern" battery in his tool pouch, only to have it discharge smoke an hour later, after the battery terminals had been shorted together by a wrench handle!
No, Ohm's Law is not being cheated here: short a voltage source with a 0 Ω conductor will not result in infinite กระแสไฟฟ้า, because there are other sources of resistance in such a circuit. The task here is to determine where those sources might be, and how they could be located.