I'm sure there are official standards, but line voltage in the U.S. is generally 110-120V ±5-6%. Edison's first power plants produced 110V DC, and this voltage more or less stuck. After WWII, 117V was adopted as the standard. Today, 120V is the target voltage for most power companies. Power companies regulate the voltage based on load, and adjustments can take a few minutes. Minor variations in line voltage usually don't cause problems. Equipment that requires precise voltages uses regulated power supplies. Frequency is more tightly controlled, originally so that clocks with synchronous motors stayed within a few seconds of the correct time.
I'm surprised people say it's 110V-120V. I worked for a utility in the U.S. and we were limited to 120V ±5%. My own outlets read 120-123V. Maybe there's some WWII construction that's still 110V but I haven't seen for myself. On all other points this is 100% correct. Frequency is very close to 60.0 Hz, much tighter than 5%. Old computers and clocks also used it for time.
@@bnorton916 Yep! They have a transformer, rectifier and filtering capacitor to smoothen out the voltage. Newer ones use a switching converter which can be much smaller and more efficient, but it is much more complicated.
The AC hasn't passed through the diodes to rectify the AC to DC yet. What you see is the AC voltage after being reduced from the power outlet ~120V to ~10V from the transformer. Yes, most wall worts are but you can buy ones with just a transformer like what you see done here.
I'm in awe of the extreme danger on display while using cheap as possible equipment and buying a transformer on Amazon versus an official distributor. Jameco is fine, if it's real.
