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Kathy Loves Physics – Why the U.S. uses 120 volts and not 220 volts

An evening pause: Here’s a bit of technology history that still affects us daily.

Hat tip Tom Biggar.

Conscious Choice cover

Now available in hardback and paperback as well as ebook!


From the press release: In this ground-breaking new history of early America, historian Robert Zimmerman not only exposes the lie behind The New York Times 1619 Project that falsely claims slavery is central to the history of the United States, he also provides profound lessons about the nature of human societies, lessons important for Americans today as well as for all future settlers on Mars and elsewhere in space.

Conscious Choice: The origins of slavery in America and why it matters today and for our future in outer space, is a riveting page-turning story that documents how slavery slowly became pervasive in the southern British colonies of North America, colonies founded by a people and culture that not only did not allow slavery but in every way were hostile to the practice.  
Conscious Choice does more however. In telling the tragic history of the Virginia colony and the rise of slavery there, Zimmerman lays out the proper path for creating healthy societies in places like the Moon and Mars.


“Zimmerman’s ground-breaking history provides every future generation the basic framework for establishing new societies on other worlds. We would be wise to heed what he says.” —Robert Zubrin, founder of founder of the Mars Society.


All editions are available at Amazon, Barnes & Noble, and all book vendors, with the ebook priced at $5.99 before discount. The ebook can also be purchased direct from my ebook publisher, ebookit, in which case you don't support the big tech companies and I get a bigger cut much sooner.


Autographed printed copies are also available at discount directly from me (hardback $24.95; paperback $14.95; Shipping cost for either: $5.00). Just email me at zimmerman @ nasw dot org.


  • Jay

    She has the history correct. I know she is explaining to a general audience about current, voltage, frequency, and 3-phase transmission. One nitpick, on her equation for the line voltage of a 3-phase Wye, it is 1.73 not 1.72. ;)

  • Andi

    Another small nit – she starts off explaining about Edison and DC, but then starts talking about transformers, but didn’t mention that they only work on AC.

  • Jeff Wright

    On Mars, we might start all over again, maybe with superconducting DC that can send information for less birdnesting.

  • When living in the UK. 220V. Electric blankets: nope.

  • MadRocketSci

    I wonder about the 60Hz thing: If it were double that, your transformers could get away with being smaller/lighter. I think Navy ships use different voltages/frequencies for losses and efficiency. (They have (450, 120) V lines at (60, 400) Hz). The 400 Hz banks are for powering various systems related to the weapons systems.

  • foxbat

    She is an amazing teacher

  • Jay

    The old standard is 4180v 60Hz for a ship’s main electrical bus, and the new Ford Class Supercarriers are using 14kv. I know that since I had to design a substation to provide ship to shore power to switch between the two.
    Yes the Navy uses 400Hz for most large motors and generators on a vessel. You can have smaller transformers with 400Hz compared to 60Hz, the less weight the better on a vessel. When you have a higher frequency, the size of the iron core and wiring of the transformers decreases.

  • Mitch S.

    Interesting topic but hard to watch.
    I’m guessing she is/was a teacher/lecturer used to speaking at the front of a large classroom/lecture hall.
    In such a setting the vocal projection and hand movements work.
    She’s not the only YouTuber to forget that typical YouTube camera distances are akin to speaking to someone a few feet away.
    Just talk, and keep your limbs under control. And avoid the facial close-ups, we aren’t your dentist! (at least she doesn’t do that)
    And when doing a video you can leave the photo or chart on screen and continue to talk. There are excellent YouTube vids where the speaker is not seen at all (Drachinifel’s naval history vids come to mind). That way there is more time for the audience to view those charts and photos
    Rant complete!

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