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Re: [Phys-l] light bulbs


On 2011, Mar 09, , at 07:30, DMathies@tulsacc.edu wrote:

V vs I gives a fairly linear curve in
the range of 30 to 110 V. The range 0 to 30 is not linear. Did not go
above 120 V because the filaments burn out.


According to the graph on p. 201 (Levi Applied Optics 1968), the life of a W gas filled lamp is reduced to half by an over "voltage" of ` 7%. 20% to about one thirteenth. Then "light output" is doubled and the efficacy almost tripled. Hence the sale of Si-halogen lamps. I'd run one to 20%, as not expensive, yet.

The characteristic sub and super linear I (V) predicts the behaviour WRT sudden failure.

Also given in Levi are exponential relations for current, resistance, power, luminous emission, efficacy, etc. as a function of the applied EMF.

For 40 to 150W the exponent is 0.523; 200 +, 0.543, e.g. i = i(0)(V/V(0))^0.523 where the approximation is good over the range 80=>130%


bc thinks using a Si- halogen lamp would be instructive.