Hunter is studying a new form of plastic chip that can be added onto a credit card, linking it to a bank account separate from the main card. This chip works by passing an electric current through a sensing coil. What application of solid-state physics is Hunter most likely working with?

The chip works by passing electric current through a sensing coil, which involves the relationship between electricity and magnetic fields. That application is electromagnetism, so the correct choice is electromagnetism. Metallurgy studies metals, crystallography studies crystal structures, and quantum mechanics describes behavior at the atomic and subatomic scale.

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