We have a long, cylindrical wire carrying a constant current $I$ in an inertial frame. At a distance of $R$ from the center of the wire, the magnitude of magnetic field is $μI/2 \pi R$. What is the magnitude of magnetic field in another inertial frame moving at a certain speed opposite to the direction of electric current?
Since the observed drift speed of the electrons is now greater, does this mean that the current as observed from this frame is greater?
If so, what about the magnetic field due to this current? Does this change too?
In general how do currents vary between different frames of reference?