In order to create an electromagnet, you would ?

Electromagnet is an temporary magnet produced when electric current is passed through specific materials.

The process of production of electromagnet is explained as follows :

From Oersted's law, we know that a current carrying conductor produces a magnetic field around it.

The same principle is applied in the production of electromagnet.

A ferromagnetic material is wound by insulated copper wires. The current is allowed to pass through wounded ferromagnetic material which in turn, produces magnetic field around it, and acts just like a strong electromagnet.

The magnetism is retained as long as there is current flow in the wire.

.) the observation by semmelweis that more mothers died of childbed fever when their doctors also worked in the morgue

+15-35=-20

going in opposite directions