What would happen if the battery from an electromagnet was disconnected and attached the wires to the opposites ends of the battery?

If the battery from an electromagnet is disconnected and then the wires are attached to the opposite ends of the battery, the current would flow in the reverse direction through the coil of the electromagnet. This would cause the magnetic field to reverse polarity. Depending on the specific setup, it could lead to a temporary disruption in the magnetic field, potentially affecting any nearby magnetic materials or devices. However, the electromagnet itself would still function, just with an opposite orientation of its magnetic field.