Timeline for Why is a replaced bulb in this strand of Christmas lights dimmer than the original?
Current License: CC BY-SA 4.0
6 events
| when toggle format | what | by | license | comment | |
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| 11 hours ago | comment | added | hobbs | In this example with only 4 bulbs the 250mW ones are also running noticeably above their power rating due to the decrease in the total string resistance — about 309mW each. But in a 50-bulb string, the effect would be much less noticeable (only a couple percent, well within tolerance). | |
| yesterday | comment | added | Spehro 'speff' Pefhany | OP: @Proph You have the simplified version in the two answers and it should make sense. In reality it's an even more pronounced effect because the bulbs don't behave like simple resistors-- they have a much lower resistance when cold. Also the lumens vs. current curve is nonlinear with much more brightness (and efficiency - but shorter life) at higher currents. Lots of gory details in this set of answers and references. | |
| yesterday | comment | added | Proph | You're right I just did the math and it works out. I'm so grateful for these answers. What a help in shining light on what's going on here. Thank you all very much and Happy New Year!! | |
| yesterday | comment | added | the busybee | @Proph brhans does not say that the .42W bulb gets 2.5V, just that it gets 100.8mA. Apply Ohm's law, and you will see.. | |
| yesterday | comment | added | Proph | Thank you! This makes sense too. The poster above you mentioned that it gets less current but the same voltage but your diagram says it doesn't get the voltage it wants either. I guess they're both right? | |
| yesterday | history | answered | Transistor | CC BY-SA 4.0 |