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Electromagnets are created by
a. applying a charge to a magnetic material, wrapped in an insulator, which creates an electromagnetic field around the magnet.
b. covering a magnet with insulation and applying an alternating electrical current to the magnet.
c. twisting a ferromagnetic material, wrapping in an insulator, and applying a direct current to the coil
d. wrapping an insulated wire around a metal with ferromagnetic properties and applying an electric current.