I have noticed on some power cables there is a quot;bumpthat the cable is wrapped around what looks like a magnet. Why?
also referred to as a Torroid which in agreement with the other responses, is an interferrece restrictor
It is not actually a magnet.It is ferrite core which helps in limiting the inrush current through the cable.
it's called a ferrite choke and are used in a wide range of prevention of electromagnetic interference (EMI) and radio frequency interference (RFI) from power supply lines and for prevention of malfunctioning of electronic equipment.
