DC 12V KK-P20/15 3KG Lifting Solenoid Electromagnet

The polarity of the electromagnet is determined by the direction of the current.  The north pole of the electromagnet is determined by using your right hand.  Wrap your fingers around the coil in the same direction as the current is flowing (conventional current flows from to -).  The direction your thumb is pointing in the direction of the magnetic field so north would come out of the electromagnet in the direction of your thumb.  DC electromagnets are principally used to pick up or hold objects