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. Some touch sensitive switch designs simply look for a change in radio-wave reception that occurs when the switch is touched. Touch sensitive lamps almost always use a fourth property of the human body - its capacitance.
Capacitance is the capacity an object has to hold electrons.
The lamp, when standing by itself on a table, has a certain capacitance. 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. They work on the same principle. Inc. All rights reserved.