How do currents flow in one direction in DC generators?

second gif is DC generator positive terminal is red color near to south pole, when coil rotate coil terminal near south pole is come contact with same brush, this module is commutator, process is called commutation. read more

A DC generator (or a DC motor) contains some means of reversing the current according to the position of the rotor. In the traditional design this is a commutator armature. A set of contacts rotate with the rotor, and brushes convey the current to them. read more

The copper oxide side put up a great opposition to the flow of current in the other direction AC current Can be rectified (changed to DC/converted) in large cooper oxide rectifiers because The cooper oxide rectifier side allow the current to flow in only one direction. read more