Reading lots about cell phone technology but the unanswered question that keeps popping up to me is how do they vibrate? — Alan, Winnipeg, Canada
Cell phones vibrate in the same way that a “Tickle Me Elmo” doll vibrates. In the case of a cell phone there is a tiny electric motor inside the phone. Attached to the motor is an off-center weight. When the motor spins, the off-center weight vibrates just like a tire does when it is not balanced properly. It is a very effective way to create vibration. To see a photo of this arrangement, see: How does a vibrating cell phone or pager work?