Dynamo in Patterdale

We went to climb Place Fell at Patterdale. You can just about see it in the background. A rarer sight was this wonderful bicycle dynamo. They are very out of fashion. I had one when I was little. The idea is that the small wheel rubs on the tyre and turns a coil in the larger silver cylinder. There is also a permanent magnet in the cylinder. The rotating coil cuts the flux of the magnet. By Faraday's Law, the size of the induced emf is directly proportional to the rate of flux cutting. If you pedal faster, the rate of flux cutting is bigger and the induced emf is bigger. In other words, the light shines more brightly. This is a disadvantage of the system. Also, the light goes off completely when you stop. I have just read that this should properly be called a magneto because it does not contain a commutator to make the current go in one direction like a proper dynamo: this produces a.c.