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A magnet with only a north pole (a magnetic monopole) can be obtained by which of the following?
Cut a bar magnet in half and keep the north pole half.
By putting a steel thumbtack on the north pole of a strong magnet. Then removing the thumbtack after it has been charged "north" by conduction.
First, wrap a coil of wire around an unmagnetized iron bar. Second, apply an alternating current through the wire. Third, quickly stop the current.
Depending on the part of the cycle the alternating current is in, the entire iron bar could be either a north pole or south pole (or have both poles).
Repeat, until the iron bar is a north pole.
A magnet with only a north pole does not exist.