A metal rod is placed along the axis of a solenoid carrying a high-frequency alternating current. It is found that the rod gets heated. Explain why the rod gets heated?

The solenoid carrying a high frequency alternating current generates a continuously changing magnetic field across the rod placed along the axis. Due to this varying magnetic field across the rod, eddy currents are generated on the surface of the rod. The resistance of the rod and the eddy currents flowing on the rod are responsible for the generation of heat.