Bulding a bicycle electricity generator helps to understand how it is possible to produce electricity from a magnet, a copper wire coil and a movement. This technique found in traditional bicycle dynamos is also used in electric power stations.
Unfortunately less bicycles are equiped with dynamos and systems powered by batteries are used instead, especially for red flashing rear lights.
This project shows a clever solution that avoids the use of batteries which contain chemical products and are quite expensive. Unlike a traditional bicycle dynamo, friction is limited as there is no direct contact with the wheel.