What law determines that induced voltage currents will flow to oppose their action?

Lenz's Law is fundamental in understanding how induced currents behave in response to changes within a magnetic field. It states that the direction of induced current is such that it opposes the change in magnetic flux that produced it. This is a consequence of the conservation of energy principle, which asserts that energy cannot be created or destroyed but can only be transformed from one form to another.

When a changing magnetic field induces an electromotive force (EMF) in a conductor, the induced current flows in a direction that creates a magnetic field opposing the original change. This means that, for example, if the magnetic field through a loop of wire is increasing, the induced current will flow in a direction that creates a magnetic field opposing that increase, effectively resisting the change.

Understanding this law is essential in various applications of electromagnetism, such as in electric generators, transformers, and inductors, where the behavior of inductance is crucial for their operation.