The relationship between the electric field (E-field) and magnetic field (B-field) in an electromagnetic wave is governed by Maxwell's equations, which describe the behavior of electric and magnetic fields in the presence of charges and currents.
In an electromagnetic wave, the electric and magnetic fields are perpendicular to each other and also perpendicular to the direction of wave propagation. The changing electric field induces a magnetic field, and the changing magnetic field induces an electric field. These changes occur simultaneously, resulting in a self-sustaining wave.
The phase relationship between the E-field and B-field depends on the specific wave's polarization. In a plane-polarized electromagnetic wave, the E-field and B-field are in phase with each other. This means that when the E-field reaches its maximum (E_max), the B-field also reaches its maximum (B_max) at the same point in space and time.
Now, let's consider the case of a propagating electromagnetic wave, such as a radio wave or light wave, passing through space. The wave does not require the presence of a current-carrying conductor or a maximal current to propagate. In fact, electromagnetic waves can propagate through a vacuum, where there is no medium to carry a current.
While it is true that a changing electric field can induce a magnetic field through the process of electromagnetic induction, this does not necessarily mean that a strong magnetic field implies a maximal current. In an electromagnetic wave, the changing electric and magnetic fields are self-propagating and sustain each other, without the need for a current source.
Therefore, the phase shift of π/2 (90 degrees) between the E-field and B-field does not depend on the strength of the magnetic field or the presence of a maximal current. Instead, it is a fundamental characteristic of the wave's polarization and the nature of electromagnetic waves as described by Maxwell's equations.