Assertion (A) : The cylindrical soft iron core in a moving coil galvanometer only makes the magnetic field radial and does not affect the strength of the magnetic field.
Reason (R) : In a moving coil galvanometer, the plane of the coil is always parallel to the magnetic field.
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A radial magnetic field ensures that the deflecting torque remains constant and independent of the rotation angle (\(\theta = 90^\circ\) relative to the area normal), which creates a linear scale on the galvanometer display (\(I \propto \alpha\)). The soft iron core serves a dual purpose: it makes the field radial and boosts the field strength.