Electric motor:

(i) It converts electrical energy into mechanical energy.

(ii) It works on the principle of magnetic effect of electric current, i.e., when a current carrying conductor is placed perpendicular to the direction of magnetic field, it experiences a force. The direction of force can be found by using the Fleming's left hand rule.

(iii) Armature is rotated in the magnetic field by supplying electric current to it by some external source such as battery to get the mechanical work.

(iv) Split ring is used as a commutator to reverses the direction of flow of current and direction of force acting on the arms of the coil after every half of its rotation. This makes the coil to rotate continuously in the same direction.

Electric Generator:

(i) It converts mechanical energy into electrical energy.

(ii) It is based on the electromagnetic induction, i.e., current  can be induced in a coil by moving it in a magnetic field. The direction of induced current can be found by using the Fleming's right hand rule.

(iii) Armature is rotated in the magnetic field by some external mechanical force to produce electric current.

(iv) The slip rings conduct the alternating current and split ring conduct the direct current to the external circuit through the brushes.