Why might 4 plug in clocks in the same house lose the same amount of minutes each day against 3 battery operated clocks and computer?

Answer 1

The battery operated clocks have their own oscillators built into them which are reasonably accurate to within as much as 15 seconds per year, but they're somewhat subject to temperature changes. The electric clocks get their timing information usually from the `cycles per second' that the AC circuit operates. For instance, in the U.S., it's supposed to be at 60 Hertz, or, 60 cycles per second.

Depending on the load on your specific feeder line and at certain times a day, it's possible that the drain on the local generating plant is causing the turbines to slow down a but, which results in your clocks getting the wrong cycles per second and in turn, slowing down a bit.

The other option is simply that your local generation plant is just simply running too slow. Then again, the battery clocks may be operating a bit fast.

want to verify which? Go get the NIST time program for your computer and set it up to query the National Institute of Standards and Time. That's what I use. It's synchronized to the nation's cesium clock and it won't be more than a few thousandths of a second off by the time it hits your computer through the internet.