Some accelerometers use the piezoelectric effect – they contain microscopic crystal structures that get stressed by accelerative forces, which causes a voltage to be generated. Another way to do it is by sensing changes in capacitance.
The flex sensor you linked to uses flexible conductive ink printed on flexible base forming a resistor. It works when bent with the ink on the outside of the curve. When bent, the conductive layer is stretched and thus extends, resulting in reduced cross section (imagine stretching a rubber band)
Gloves used for Mute people Actions.
Speakers work by converting electrical energy into mechanical energy (motion). … In speakers, a current is sent through the voice coil which produces an electric field that interacts with the magnetic field of the permanent magnet attached to the speaker. Like charges repel each other and different charges attract.