[ExI] Thermal expansion - Ball and ring experiment

spike spike66 at comcast.net
Wed Jun 13 01:45:04 UTC 2007

The gap gets larger.  Imagine the arc piece that is missing from the ring to
form a C.  That piece of nothing expands the same way the piece of something
would have expanded were it present.  So the gap gets larger as the C is


> -----Original Message-----
> From: extropy-chat-bounces at lists.extropy.org [mailto:extropy-chat-
> bounces at lists.extropy.org] On Behalf Of Emlyn
> Sent: Tuesday, June 12, 2007 5:42 AM
> To: ExI chat list
> Subject: [ExI] Thermal expansion - Ball and ring experiment
> I was just in a "heated" discussion with a friend about a twist on the
> classic ball and ring experiment:
> http://www.physics.usyd.edu.au/super/therm/tpteacher/demos/ballring.html
> When the ring is heated, it expands, and so the hole gets larger, and
> you can pass the ball through the ring, even though the ball doesn't
> fit through the ring when the ring is at room temperature.
> The point of contention was this: What if there was a gap in the ring
> (so it is now a letter "C" shape). Will the gap in the "C" close or
> open further on heating?
> My contention is that the gap will get larger, only in that the entire
> C shape scales up as it is heated.
> My friend's contention is that the gap will become smaller, (because
> the metal expands into the gap).
> I can't find anything online even close to settling this score. We
> tried some experiments with wire rings and the gas stove top playing
> the role of bunsen burner (amazingly no one ended up branded for
> life), but it was inconclusive.
> Any pointers to anything that can settle this argument?
> Emlyn
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