Our knowledge of electromagnets developed from a series of observations. In 1820, Hans Oersted discovered that a current-carrying wire produced a magnetic field. Later in the same year, André-Marie Ampere discovered that a coil of wire acted like a permanent magnet and François Arago found that an iron bar could be magnetized by putting it inside of a coil of current-carrying wire. Finally, William Sturgeon found that leaving the iron bar inside the coil greatly increased the magnetic field.
Consider the following text:
Mark is doing an experiment creating a magnet. He takes a piece of iron named iron bar A and wraps it in a coil of copper wire. After that he puts an electric current through the copper for about an hour.

Given Mark disconnects and unwraps the copper wire, will the magnetic strength of the iron bar have increased or decreased?