A coil of insulated wire is wound many times around an iron bar. The wire is connected to a battery and a contact switch. The contact switch is alternately flipped closed and left closed, so the wire carries a current through it, and then flipped open and left open, so that the current stops. Describe what magnetic fields are created, if those magnetic fields in turn induce an emf, and whether the induced emf is in the direction of the original current or opposite to it. Justify your answer using Lenz's law and the conditions which can cause a magnetic field to
induce an emf. You may draw a diagram if it helps you to visualize the apparatus.
The Attempt at a Solution
This problem is really confusing. I understand that the apparatus is a simple circuit with a solenoid, and when turned on, an electromagnet is produced from the solenoid. However, I don't understand what the question is asking. It asks if the magnetic fields induce an emf. But why would the magnetic field created by a circuit with a battery induce an emf on itself? I thought that only external magnets not associated with the circuit could induce an emf on it. Also, I am not sure how to determine the direction of the field in relation to the current. In addition, I am not sure how Lenz's law applies because since I thought that that had to do with an external magnetic field affecting the current and the subsequent field created by the current. If I could get some pointers I would really appreciate it.