physics question #308



Edward Driedger, a 11 year old male from the Internet asks on December 17, 1997,

Q:

How do touch lamps work? If one person touches the touch pad and someone else taps his other hand, will the light still react?

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the answer

Tim Collings answered on December 17, 1997, A:

Most touch lamps work using a capacitive sensor. The dielectric field strength changes when a foreign object is brought in proximity with the switch. The capacitance is altered according to C = e*A/d where e is the dielectric, A is the cross-sectional area of the capacitor plates and d is the distance between plates.

The reason why a second person can touch the first person to make the switch work is because this, too, changes the dielectric field strength enough to actuate the switch.

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