Dirt bikes and many motorcycles also have chains, this allows you to change gears to adjust torque (alternatives include shaft and belt drives).
E-bikes can have the motors on the wheel (hub-drive) or on the pedal (mid-drive). This choice is largely related to how much you want your e-bike to really be a scooter or really be providing pedal assist. As a consequence hub-drive e-bikes typically have a throttle while mid-drive do not.
A good mid-drive e-bike really makes it feel like you are a super human cyclist rather than riding a scooter. It leads to a much smoother riding experience if your aim is to still be essentially bicycling but you'd like to get moving faster and not break a sweet even on the most extreme hills.
I have a couple of mid-drive e-bikes (Bafang motors) with throttles. Throttled mid-drives let you get the best of both worlds: Great pedal assist combined with the ability to just be a scooter when you get tired. And I agree that mid-drive is the way to go if you want to ride on hills. If you commute in San Francisco for example, a hub drive e-bike will not help you much but a mid-drive will change your life.
I could imagine (not necessarily feasible!) the pedals only moving a dynamo with variable resistance to mimic real world pedaling, and the hub drive doing the drive according to the pedaling speed? Would that be a scooter or a e-bike, according to norms?
Completely agree. They should probably just remove the pedals and generator entirely and save that weight. But then legally it becomes a scooter and probably would require a license and be more limited as to where it could go.
But what if the pedals are connected to the wheel only in a "symbolic" way, say, some electrical contact or something? So technically you still have to pedal to qualify as e-bike, just without real mechanical transmission? And if you lose power bad luck, don't commute with an empty battery...
E-bikes can have the motors on the wheel (hub-drive) or on the pedal (mid-drive). This choice is largely related to how much you want your e-bike to really be a scooter or really be providing pedal assist. As a consequence hub-drive e-bikes typically have a throttle while mid-drive do not.
A good mid-drive e-bike really makes it feel like you are a super human cyclist rather than riding a scooter. It leads to a much smoother riding experience if your aim is to still be essentially bicycling but you'd like to get moving faster and not break a sweet even on the most extreme hills.