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Thread: bulb filament

  1. #11
    Join Date
    Feb 2003
    Location
    Illinois
    Posts
    19,331
    Quote Originally Posted by ActionDave View Post
    T rating is required for DC. AC only you don't need it.
    Thanks for making the correction. I did not read the UL Guide Information for Snap Switches (WJQR) far enough.
    If the switch is an AC-DC general use switch, the "T" marking is required.
    If the switch is an AC general use switch, the "T" marking is not required.
    Don, Illinois
    "It is the first responsibility of every citizen to question authority." B Franklin

  2. #12
    Join Date
    Feb 2009
    Location
    Durango, CO
    Posts
    3,586
    You're welcome. I only knew about the rating because of some work I did on a houseboat.
    If Billy Idol or John Denver is on your Ipod go and re-evaluate your life.

  3. #13
    Join Date
    Feb 2003
    Location
    San Francisco Southbay
    Posts
    1,873
    Thank you for your replies.

    As always I learned something.
    Edward
    Education is a progressive discovery of our ignorance.

  4. #14
    Quote Originally Posted by edward View Post
    Which bulbs have a tungsten filament? All bulbs or just halogens?

    Thanks.
    Just about every incandescent and fluorescent lamps.
    Exceptions are cold cathode lamps and novelty carbon filament fluorescent lamps. The filaments in fluorescent lamps are for not just for pre-heating. They allow the cathode coating to operate at thermionic temperatures.

    Even though they're not energized, high temperature cathodes are crucial for long life and performance. When they're dimmed to the point of not being able to sustain optimal temperature, they have to be heated by energizing them or the lamp will sputter and fail rapidly.

    As for across the line type bulbs, they have a considerable inrush current. When a 500W work light is plugged in, there is a noticeable voltage drip that is enough to dim other lights on the same branch. As such, many plug-in consumer switch/control devices have three ratings, motor, resistive and tungsten. The tungsten wattage rating is lower than resistive load.

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