Figure 23-29 shows a vertical iron rod with a wire coil of many turns wrapped around its

Question:

Figure 23-29 shows a vertical iron rod with a wire coil of many turns wrapped around its base. A metal ring slides over the rod and rests on the wire coil. Initially the switch connecting the coil to a battery is open, but when it is closed, the ring flies into the air. Explain why this happens.
Figure 23-29