A coil of wire has a large alternating current flowing in it. A piece of aluminum or copper placed near the coil becomes warm even if it does not touch the coil. Explain why.

Question: Explain why a piece of aluminum or copper placed near a coil of wire with a large alternating current flowing in it becomes warm, even if it does not touch the coil. Answer: The piece of aluminum or copper becomes warm due to electromagnetic induction and Joule heating. The large alternating current flowing through the coil creates a changing magnetic field, which induces eddy currents in the nearby conducting material. These eddy currents generate resistive force, and the material's electrical resistance converts the kinetic energy of the eddy currents to thermal energy, resulting in heat generation. This is why the aluminum or copper piece becomes warm even if it does not touch the coil.