Interesting non-linear effects

Bob Bruhns bbruhns at
Sat Nov 10 10:40:56 CST 2012

Looking at the chart in 'Light Bulbs.pdf', the Philips 100W 120V DuraMax 
bulb seems to display a negative temperature coefficient of resistance 
around 115V to 120V.  I didn't see this in the other bulbs that were 
listed. The magnitude of the effect is relatively small, and it reminds 
me of unexpected things that I see in many such seemingly simple 

The dip at 120.8V is probably the result of a measurement recording or 
transcribing error - if someone thought the notes said 0.89A when they 
really said 0.84A, then the resistance calculation would have shown 144 
instead of 136, and the graph would have been much more believable.  
(See attached spreadsheet.)  But maybe 0.89A was the correct reading, 
and the dip at 120.8V was real.  I sometimes wonder how much information 
is routinely ignored in day to day work.

    Bob, WA3WDR

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