Animals and their trainers. What is the main idea of the passage?

jenkins wanted the narrator to write a ghost story for his magazine. he wanted the narrator to give the readers a story based on the supernatural. he wanted him to give the readers real 'horror' stories and not the type of live ghosts which he had presented in his earlier stories.

the direction of the magnetic field produced by an electric current will change when the direction of the electric current changes. for example : if a current is flowing in a straight length of wire, the magnetic field is described by a concentric circle (using right-hand rule).