Final answer:
Eddy currents are loops of electrical current induced within conductors by a changing magnetic field and their behavior can be described using Ampère's law.
Step-by-step explanation:
The currents that flow in circles inside a disc are known as eddy currents. These are loops of electrical current induced within conductors by a changing magnetic field in the conductor, due to Faraday's law of electromagnetic induction. Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field. They can create magnetic damping and are utilized in applications like metal detectors and induction cooktops. According to Ampère's law, the magnetic field within a current-carrying conductor is given by an equation involving the current I. For a uniform current density J, this is proportional to the ratio of the current I passing through the enclosed area of a circular path to the total area.
Eddy currents are also used in braking systems for trains and roller coasters, known as magnetic damping, exploiting the resistance caused by induced currents in the presence of a magnetic field. These currents are fundamental in the working of electric generators and induction cooktops, showing their importance in both industrial applications and daily life.