An AC simulator
You've probably already noticed that there's no direct electrical connection between the two coils of a transformer. You're probably curious how you can get a steady electric current out of a transformer. This Project will show you how.
When you finish wiring, push the Key once. You'll see the Meter pointer swing to the right. Now start pressing the Key over and over. You'll notice the Meter pointer moves further to the right and doesn't fall back quite as far when you release the Key.
Now press the Key as fast as you possibly can, Can you make the Meter pointer stay all the way over 10 the right?
Probably not — but you noticed that the Meter pointer didn't swing over quite as wide a range as it did when you pressed the Key slowly.
The AC used in the power lines of a building reverses direction 120 times per second. That's the same as pressing the Key in this Project 120 times each second.
The magnetic fields in a transformer connected to an AC line change so rapidly that there's almost no noticeable "chopping" or interruption in the electricity at the transformer's output. (And here's a excercise for your brain: if you put AC into a transformer, will the output be AC or DC ? Don't peek at the answer.)