Consider an incandescent light bulb connected to a power source. One feature of
ID: 2153372 • Letter: C
Question
Consider an incandescent light bulb connected to a power source. One feature of the power is the you can adjust the amount of electrical current it supplies to the light bulb, which in turn enable you to adjust the amount of power consumed by the bulb. You initially turn on the power source and set it so that it appliesfull power to the bulb. A few minutes later, you reduce the power to 50%. For each of the following
statements, indicate whether it is true or false and why.
Question.
The efficiency of the light bulb will change. ( The efficiency of the light bulb is the amount of light radiates by the filament that lies in the spectrum what visible to the human eye)
True or false and why.
Explanation / Answer
false I'm sorry, but your "smash it" test is giving you the wrong data. While it is true that some lamps are evacuated, most ordinary incandescent lamps are filled with argon (or sometimes nitrogen). This is actually essential else the vapor pressure of the hot tungsten filament would quickly boil the filament away to nothing. (A long time ago, 15W or so and smaller mains-powered lamps tended to be evacuated and larger lamps were gas-filled. I don't know if this is still true.) Classier ordinary incandescent lamps are filled with krypton. I think this is done because the krypton conducts and/or convects less heat away from the filament, leading to higher lamp efficiency. That's why flashlights (torches) so often brag about having a "Krypton lamp!" And finally, for quartz-halogen lamps, these are actually filled with gas at quite a high pressure. You can confirm this for yourself: the packages for bare lamps always warn that the lamps must be shielded because they may explode on failure (as the resulting arc heats the filling gas and quickly raises the pressure to the bursting point).