The iron core is formed of {HEAD ~ particles} of iron or {TAIL ~ an iron based magnetic material} 
of
The iron core is formed of { HEAD ~ particles } of iron or { TAIL ~ an iron based magnetic material }
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL