{10 points) 1. 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, s0 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. Answer: {7 points) 2. Explain the mechanism by which AC (alternating current) through the primary circuit of a transformer produces an alternating voltage and current in the secondary coil. Then explain why this would or would not work with DC (non-alternating current) in the primary coil. Answer: (8 points) 3. Explain briefly how moving electric charges at an atomic level produce magnetically polarized domains in a sample of iron, and how the domain structure differs for a magnetized iron bar and one that is not magnetized