Question

Why are magnets used in cranes to separate iron objects from junk

Answer 1

Magnets and more specifically electromagnets are used to separate iron objects from junk because, i) Iron is attracted to magnets ii)The junk scrap contains mixture of different elements and particles of various substances in heterogenous (or simply in fused form) .Thus, magnet of crane easily seperates the iron particles from  the mixture simply because iron scraps get attracted to it is thus isolated from remaining junk and separated.