Iron filings 58 are sprinkled around the L shaped rod 30 and toroid magnets 42 and 44 to illustrate the modification effect of {HEAD ~ the magnetic lines} of {TAIL ~ force} 
of
Iron filings 58 are sprinkled around the L shaped rod 30 and toroid magnets 42 and 44 to illustrate the modification effect of { HEAD ~ the magnetic lines } of { TAIL ~ force }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL