Which one among the following correctly defines a unit magnetic pole in SI units ? It is the pole which when placed in air at a distance of—

In the study of magnetostatics, a unit magnetic pole is defined based on the force it exerts on an identical pole. In the CGS (centimetre-gram-second) system, a unit pole is defined as one that repels an equal and similar pole with a force of 1 dyne when placed 1 centimetre apart in a vacuum [1]. However, the question specifically asks for the definition in SI units (or the rationalized MKS system). In this system, the units of length and force are scaled to the metre and the newton, respectively. Consequently, a unit magnetic pole in the SI/MKS framework is defined as the pole which, when placed in air (or vacuum) at a distance of 1 metre from an equal and similar pole, repels it with a force of 1 newton. This definition aligns with the transition from CGS units to the international system of units.

Sources

1. [1] https://www.sciencedirect.com/topics/physics-and-astronomy/magnetic-pole