Re: pic: How Not To Do It: Electronics Edition
 

It is a perfect example. In reality, an H-Bridge is just transistors performing the same operation, just solid-state.

I guess the spark could be a possible recruiting tool -- that, only if the correct precautions are taken! It's not the best idea to try this at home, at least if the voltage is greater (or lower) than 0v :D

I think that that is actually quite a typical setup to introduce the system.

However, it's pretty cool how I still use that setup all the time. Just take a DPDT switch. Connect the middle pins to the motor. Connect one side of the switch to the battery. Connect the other side to the battery too. However, on the second side, reverse the polarity. If the switch is on one side, the motor will spin in one direction. Switch the switch and the motor will switch directions!

I am wondering what that was even meant for. Is that supposed to be a motor tester of some sort? It seems quite dangerous!

Re: pic: How Not To Do It: Electronics Edition
 

Not exactly an H bridge since the legs are not independent. However, please add a fuse or breaker to this in the future. Not the 120 amp either, it must be safely sized for the smallest wire.
While it is unlikely to cause any harm at 12 volts, this is a good demo to show what was considered "safe" 100 or more years ago. I am reminded that when the IBEW was founded in 1891, the average life expectancy of a line worker was 36. It was common practice at that time to string power cables on poles that contained live wire using horse drawn wagons with ladders mounted on them.
To use this for household line voltage please remember that 120 volts is the RMS value not the peak, which is over 300 volts.