The main difference between dynamos and alternator is the type of current they produce. The commutator constantly changes the polarity of the output current so that the output is always of the same polarity. Without a commutator, a dynamo would simply produce alternating current just like an alternator.
Also know, how does a dynamo produce energy?
Dynamos and Generators convert mechanical rotation into electric power. Dynamo - a device that makes direct current electric power using electromagnetism. It is also known as a generator, however the term generator normally refers to an "alternator" which creates alternating current power.
Can a dynamo be used as a motor?
If its stator field is a magnet yes, if it is a coiled electromagnet the armature will not start generating unless field is connencted to a battery, it will auto feed afterwards. Yes, you can use a motor as dynamo or generator.