Consider the magnetic field (B) of a wire with a constant current (I). A Magnetic Field sensor is placed at a radius (r). Will the magnitude of the magnetic field change if the sensor was moved around the wire while holding the current and radius constant?

No, the magnitude of the magnetic field won't change.

Explanation:

The magnetic field produced by a wire with a constant current is circular and its flow is given by the right-hand rule. Since this field is circular with center on the wire the magnitude of the magnetic field around the wire will be given by B = [(\mi_0)*I]/(2\pi*r) where (\mi_0) is a constant, I is the current that goes through the conductor and r is the distance from the wire. If the field sensor will move around the wire with a fixed radius the distance from the wire won't change so the magnitude of the field won't change.

scientific laws are the result of testing theories and proving them to be facts.