We applied a time-varying voltage across a light bulb and we measured the curren

Question

We applied a time-varying voltage across a light bulb and we measured the current as explained in this video:

https://www.youtube.com/watch?v=EiNy7PbykME

Produce two graphs. One graph should show the resistance of the bulb as a function of applied voltage for volts from 0 volts to 2.5 volts as the voltage increased from 0 to 2.5 volts. The second graph should show the resistance of the bulb as a function of applied voltage from 0 to 2.5 volts with values obtained as the voltage decreased from 2.5 volts to 0. You can calculate resistance values based on the data shown in the video.

Comparing the two graphs, the assignment is to explain to the reader why the voltage/current relationship for the light bulb also seems to depend on the history of the applied voltage as shown in the video. In other words the resistance values for the bulb depend on the applied voltage and whether or not the applied voltage was incresing of decreasing. In your attempt to explain this, site references to support your explanation.

(Note: there is a mistake at 2:51 into the video. The audio refers to ".6 amps" when it should say "0.52 amps")

Explanation / Answer

This phenomenon can be understood as the variation in resistance of filament bulb with change in temperature. When we are coming down from 2.5 volt to zero, bulb filament is heated more (high temperature) so in turn shows high resistance. Unlike while going up, it is comparatively cooler , shows less resistance.

I hope this was clear.

Feel free to ask related queries below. Thank you..

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