Lionel has a great Youtube video on " phasing two transformers to be used together".
It's linked all over the forum and an easy search on youtube.
I highly suggest watching it even you never plan on using two together. Mike does a great job on a very simplified sine wave expaination of phasing.He is easy to listen to also
The sine wave pictures make it easy to understand a few things about the raw basics of AC. If I was training another random 16yr old for coin-op gameroomt assistant I'd make watching it a requirement.
(an oscilloscope picture is just a real time graph. They may look intimidating but it's just up or down volts and how fast. )
An interesting note, a bulb may run cooler and last longer on ac because the voltage is closer to, or at zero volt for a fleeting "rest period" at 60hz (60 waves per second)