Physics Demo Number: 012 |
Approximate Run Time: 8 min |
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Temperature Coefficient of Resistivity |
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Demo DescriptionMeasure the resistance of incandescent light bulb filaments, in both their room temperature state and as a function of time immediately after they are switched off. |
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Scientific Principles
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Equipment LocationAll the components live in Kit (012) on [B-2-4]. On occasion the digital multimeter may be in Kit (051) on the middle shelf of cart at end of [A-B] row next to library wall.
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Equipment
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InstructionsPhotos shows apparatus for measuring resistance of incandescent light bulb filament both in its room temperature state and as a function of time immediately after it is switched off. The bottom photo shows the basic hookup of the multimeter. The top left photo gives a view of the lamp hookup. The top right shows the dedicated switching hardware. The bottom photo shows the output stage of the multimeter on the right , which may be placed on the overhead in the lecture room to let the class see the resistance values of the bulbs as a function of time after being switched off. There is a carbon-filament bulb (whose resistance goes down when heated) in the brown cardboard carton in the bottom left photo. For a given bulb, when the room temperature resistance is measured, one should slide the meter switch to" range- hold", so that a larger range of the transient resistances during the cooling cycle can be seen on the overhead projection screen. SAFETY WARNING: Exercise great caution in showing this demo as there are bare conductors somewhat available with 120 VAC on them at times! |
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Writeup created by David A. BurbaCopyright © 2013, Vanderbilt University. All Rights Reserved. |
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