Electrons and Electric Fields

The famous Millikan oil-drop experiment involved observing suspended minute oil-drops falling under gravity and then under an applied electric field which stopped the downward motion. There are quite a few descriptions of the experiment on the Internet, this being one of many.

There is a wee, ever so minor problem with the experimental setup and assumptions. This wee problem is the assumption that with the experimental electric field turned off, the only force acting on the oil-droplets is gravity.

What about the ambient electric field of the Earth itself?

None of the descriptions of the experiment make any mention of the Earth’s electric field, but do stress the presence of the far weaker gravitational field, and of course the far stronger electric field induced by the experiment design to stop the oil-droplets from falling under gravity.

About Louis Hissink

Retired diamond exploration geologist. Trained by Western Mining Corporation and polished by De Beers.
This entry was posted in Geophysics. Bookmark the permalink.

One Response to Electrons and Electric Fields

  1. cadxx says:

    I’ve always meant to do a web page on the Millikan oil-drop experiment but never gotten around to it. When I was in college academia the most common complaint among lecturers was that scientific experiments don’t work and I’m led to believe that Millikan falls into this category. Mainstream science of course refers to this as bad methodology but I’m not so sure. As I understand it Millikan was kinda selective on the subject of which results to publish.
    It’s all there in the history if you can find it!


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