Whilst a motor turns in magnetic field there is relative movement between the field and armature which creates an emf as shown by Faraday. Lenz's Law shows that this emf will be in a direction as to oppose the cause and hence it travels opposite to the current flowing through the motor giving it the name back emf.
nice try but those 2 are a different part of the assignment (the only other part I haven't mantioned is the bibliography so any more suggestions will probably be good),