Question

what is meant bylow coercivity and low retentively?

Answer 1

Low coercivity of a magnet shows that it will loose its magnetism rapidly, i.e., its magnetisation can be erased by stray magnetic field, temperature changes or mechanical damage due to rough handling etc.

Soft iron which is used to make electromagnet has low retentivity. When a soft iron rod is placed in a solenoid and current is passed through the solenoid, magnetism is produced in the soft iron. When the solenoid current is switched off, the magnetism is removed instantly as retentivity of soft iron is very low.