Hi Fareena
All magnetisim is due to moving charges. The best way to think of why all magnets have two poles is to think of a coil of wire with a current in it. This will create a magnet very much like a bar magnet. In the coil, one end is the North pole and the other end is the South pole. Now you can see that the coil must have two poles because it must have two ends. Cut the coil in half and it still has two ends. Cut the coil down to one loop and it still has two ends. Even in a bar magnet the magnetism is due to the orbiting electrons in the material. One side of the orbit is one pole and the other side is the other pole and there is no way to have an orbit without two sides.
Now if magnetisim had magnetic charges ,like electricity does, then you could have magnetic monopoles but no one has ever found a magnetic charge.
CHEERS
BEST OF LUCK FOR YOUR EXAMS
