Question

the function of concave cylindrical magnet in dc dc electric motor

Answer 1

Armature is a soft iron core on which a coil having a large number of turns of insulated copper wire is wound. Magnetic poles are concave and cylindrical. The concave poles produce a radial magnetic field.

Answer 2

Armature : It contains rectangular coil made of insulating copper wire wound on a soft iron core. The coil wound on the soft iron forms armature. The coil is mounted on an axle and is placed between the cylindrical concave poles of magnet to produce magnetic field.
Motor Principle: When an electric current passes through coil in magnetic field, the magnetic force produces a torque which turns the shaft of DC motor.