Creating direct current (D.C.)
We can create a direct current from the mechanical movement of turning around a handle inducing a current in the wires.
Producing a direct current this way means the voltage produced does not reverse but moves to zero and back again to a peak flow.
We can use Flemings right hand rule.
Right = Induced
Flemings right hand rule shows us the direction of the current in the wire below.
When the handle has been spun 180° you can see the direction of the current in the wires within the magnetic field have reversed. But the direction of the current flow into and out of the galvanometer remain the same due to the commutator.
The galvanometer will still show a movement from a peak back to zero and back up to the peak. Never does it reverse direction.
If you were to plot the voltage change through time for one complete 360° revolution of the handle you would find the following.
Or (depending which way you turn the handle.)
NOTE: Point `A` is where the wires within the magnetic field are vertically aligned. Point `B` is at the first diagram. Point `C` is at the second diagram.