# Touch lamp **URL:** \ **Category:** Factual Questions\ **Created:** [March 29, 2000, 2:53am UTC](https://boards.straightdope.com/t/touch-lamp/9385 "2000-03-29T02:53:00Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Freejack00](https://avatars.discourse-cdn.com/v4/letter/f/b9e5f3/32.png) [@Freejack00](https://boards.straightdope.com/u/Freejack00)\ **Post date:** [March 29, 2000, 2:53am UTC](https://boards.straightdope.com/t/touch-lamp/9385/1 "2000-03-29T02:53:00Z")
How do the type of lamps you touch to turn on & off work? Some people have told me by means of a ground. Crazy as I am I tried jumping up when touching the damn thing and it still goes on. Can one of you dopes help, my sanity and my floor are at stake!! 🙂 ---
**Author:** ![Ursa\_Major](https://avatars.discourse-cdn.com/v4/letter/u/a88e57/32.png) [@Ursa\_Major](https://boards.straightdope.com/u/Ursa_Major)\ **Post date:** [March 29, 2000, 3:33am UTC](https://boards.straightdope.com/t/touch-lamp/9385/2 "2000-03-29T03:33:00Z")
There are basically three different ways that various touch-lamps work: From [http://www.howstuffworks.com/question42.htm](http://www.howstuffworks.com/question42.htm) > [@](#): > > Temperature - The human body is generally warmer than the surrounding air. Many elevators therefore use buttons that are sensitive to the warmth of the human finger. These buttons, of course, don’t work if you have cold hands. They also have the unfortunate property of taking an elevator to a floor where a fire is burning. The motion-sensitive lamps you see on people’s patios also sense the heat of the human body. > > Resistance - The human body, being made mostly of water, conducts electricity fairly well. By placing two contacts very close together, your finger can close the circuit when you touch it. > > Radio reception - you may have noticed that, when you touch an antenna, the reception gets better on a TV or radio. That’s because the human body makes a pretty good antenna. There are even small LCD TVs that have a conductive neck strap so that the user acts as the antenna for the TV! Some touch sensitive switch designs simply look for a change in radio-wave reception that occurs when the switch is touched. ---
**Author:** ![Ursa\_Major](https://avatars.discourse-cdn.com/v4/letter/u/a88e57/32.png) [@Ursa\_Major](https://boards.straightdope.com/u/Ursa_Major)\ **Post date:** [March 29, 2000, 3:36am UTC](https://boards.straightdope.com/t/touch-lamp/9385/3 "2000-03-29T03:36:00Z")
Boy, did I blow that. The part after that which I quoted: > [@](#): > > Touch sensitive lamps almost always use a fourth property of the human body - its capacitance. The word “capacitance” has as its root the word “capacity”. Capacitance is the capacity an object has to hold electrons. The lamp, when standing by itself on a table, has a certain capacitance. This means that if a circuit tried to charge the lamp with electrons, then it would take a certain number to “fill it”. When you touch the lamp your body adds to its capacity. It takes more electrons to fill you and the lamp, and the circuit detects that difference. It is even possible to buy little plug-in boxes that can turn any lamp into a touch-sensitive lamp. They work on the same principle. ---
**Author:** ![SingleDad](https://avatars.discourse-cdn.com/v4/letter/s/9e8a1a/32.png) [@SingleDad](https://boards.straightdope.com/u/SingleDad)\ **Post date:** [March 29, 2000, 5:26am UTC](https://boards.straightdope.com/t/touch-lamp/9385/4 "2000-03-29T05:26:00Z")
Great link, UM! That’s going to find its way to my home page next time I update it! 🙂 ---
**Author:** ![EvilGhandi](https://avatars.discourse-cdn.com/v4/letter/e/f17d59/32.png) [@EvilGhandi](https://boards.straightdope.com/u/EvilGhandi)\ **Post date:** [March 29, 2000, 12:42pm UTC](https://boards.straightdope.com/t/touch-lamp/9385/5 "2000-03-29T12:42:00Z")
Papa, I know your response was mostly a C/P from a Cecil wannabe, (shameless asskiss) but how in heavens name could this be true? Ursa Major Quote, (of his quote) “They also have the unfortunate property of taking an elevator to a floor where a fire is burning” Are the sensors in or near the buttons? Seems to me I would be a lot warmer than a fire on the 23 floor. Specially if Tyra Banks or Christie Brinkly was to board with me in the lobby. ---
**Author:** ![handy](https://avatars.discourse-cdn.com/v4/letter/h/b5a626/32.png) [@handy](https://boards.straightdope.com/u/handy)\ **Post date:** [March 29, 2000, 3:20pm UTC](https://boards.straightdope.com/t/touch-lamp/9385/6 "2000-03-29T15:20:00Z")
Wet some paper & touch it with the paper & see if it goes on. Mine do. ---
**Author:** ![Arjuna34](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)\ **Post date:** [March 29, 2000, 3:49pm UTC](https://boards.straightdope.com/t/touch-lamp/9385/7 "2000-03-29T15:49:00Z")
There was a thread here a few weeks ago about elevators with heat-sensitive switches taking people to burning floors. Apparently this has actually killed someone. The biggest problem with them though is that, especially during a fire, they are are unpredictable. It may not take you directly to a burning floor, but it may not take you to the ground floor either. I don’t know how they worked, but someone posted in the earlier thread who seemed to be either in the elevator or fire-fighting industry. Arjuna34 ---
**Author:** ![VileOrb](https://avatars.discourse-cdn.com/v4/letter/v/9e8a1a/32.png) [@VileOrb](https://boards.straightdope.com/u/VileOrb)\ **Post date:** [March 29, 2000, 3:54pm UTC](https://boards.straightdope.com/t/touch-lamp/9385/8 "2000-03-29T15:54:00Z")
EvilG - It’s not the button in the elevator that takes it to the burning floor it’s the call button on the burning floor. You can press all the buttonns in the elevator and they will light up nicely but the elevator will still have been summoned to the burning floor. ---
**Author:** ![EvilGhandi](https://avatars.discourse-cdn.com/v4/letter/e/f17d59/32.png) [@EvilGhandi](https://boards.straightdope.com/u/EvilGhandi)\ **Post date:** [March 30, 2000, 8:02am UTC](https://boards.straightdope.com/t/touch-lamp/9385/9 "2000-03-30T08:02:00Z")
Ahha the call button on the burning floor, that makes sense. I probably should have figured that all by myself. Let that stand as reason #15 not to post and drink beer at the same time.