Metropolitan Transportation Authority (MTA) Electrical Practice Test

Eddy currents are circulating currents that form inside a conductor when the magnetic flux through it changes. According to Faraday’s law, a changing magnetic field induces an emf around closed paths in the material, so currents loop within the conductor. These currents generate their own magnetic fields that oppose the original change in flux (Lenz’s law), and they tend to cause heating and energy losses in electrical equipment. The other terms don’t describe this internal looping current: the Faraday effect is about rotation of light’s polarization in a material, magnetic braking is a use of those currents to slow motion, and inductive coupling refers to energy transfer between circuits via mutual magnetic fields rather than currents circulating inside a single conductor.