Iron attraction and directivity. The non-magnetic nature of medical wires can be judged by the wire's iron attraction and directivity. Put the steel needle close to the iron filings. If it can attract iron filings, the steel needle is magnetic. Or tie the middle of the steel needle with a thin wire and hang it. When it is stationary and always points in the north-south direction, the steel needle is magnetic. Wire is a kind of medical equipment widely used in modern medical treatment, often used in interventional therapy, cardiac pacing, catheterization and other fields.