Which law states that an induced emf produces a magnetic field opposing the change that induced it?

Lenz's law describes how an induced electromotive force (emf) creates a magnetic field that opposes the change in magnetic flux that caused the induction. This principle is essential in electromagnetism, as it reinforces the conservation of energy. When a magnetic field changes within a closed loop, inducing an emf, the resulting current will flow in such a direction that its magnetic field counteracts the original change. This behavior ensures that the system resists alterations in the state of magnetic flux, aligning with the idea that energy must be conserved in physical processes.

This understanding plays a crucial role in applications such as electric generators and inductors, where controlling the interaction between magnetic fields and currents is vital for their operation.