Question

what is the operation of dc motor?

Answer 1

A DC motor consists of a wire inside an external magnetic field. When a current is applied to the wire it produces its own magnetic field, the stronger the current the stronger the magnetic force. Like in two bar magnets, like charges repel. So where the magnetic field lines of the current carrying wire cross the field lines of the external magnetic field there is a repulsive force, this force moves the wire. In a motor the wire would be a loop so that when it is repelled the other half of the loop cuts through the field of the external magnet creating a constant force (i.e. the metal loop will constantly spin). The loop would then be connected to what ever it is you wish to drive (a whisk for example lol), so that when ever there is a current applied to the loop, the loop will spin.
Flemming's left and right hand rules can be used here to understand the directions of the magnetic fields and also the direction of motion.

Bit long winded i think lol sorry but hopefully you see when i mean. This is the first question i've answered so may have to work on clarity.