Which concept explains why a magnetic field opposes changes in current?

The concept that explains why a magnetic field opposes changes in current is Lenz's law. This principle states that the direction of the induced electromotive force (emf) and the current produced by that emf is such that it creates a magnetic field opposing the change that produced it. Essentially, when there is a change in magnetic flux through a circuit, Lenz's law helps to maintain conservation of energy by ensuring the induced current works against the change in the magnetic environment.

For example, if the magnetic field through a loop of wire increases, the induced current will flow in a direction that creates a magnetic field counteracting the increase. This opposition to changes in magnetic flux is fundamental to the behavior of inductors in electrical circuits and is a key aspect of electromagnetic induction.

Other laws, such as Faraday's law, relate to the magnitude of the induced emf but do not directly explain the opposition aspect. Ohm's law, which describes the relationship between voltage, current, and resistance, does not address magnetic fields or currents induced by changes in magnetic flux. Kirchhoff's law provides rules for current and voltage in electrical circuits but does not focus on the behavior of magnetic fields in relation to changing currents. Thus, Lenz's law is the