Lenz's Law
A physical law asserting that the direction of an induced current always produces a magnetic field that opposes the change in magnetic flux that induced it.
Governing formula
Represented by the negative sign in E = -dΦ_B/dt
SI unit
Dimensionless (Directional Law)
In depth
Lenz's law is a direct manifestation of conservation of energy. If the induced field reinforced flux changes, it would create an infinite energy feedback loop without external work.
Examples in the real world
A strong neodymium magnet dropped down a thick copper tube experiencing electromagnetic drag force and falling at a slow terminal speed.