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1. Free Space

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   Prior to 2019, $\mu_0$ was defined as exactly $4\pi \times 10^{-7} \ \text{N/A}^2$. Its current derived value is approximately $1.2566 \times 10^{-6} \ \text{H/m}$ (henries per meter).
   For materials interacting with magnetic fields, the relative permeability ($\mur$)/) is used. For free space, $\mu_r$ is defined as exactly 1. This adherence to unity is crucial for classifying materials as diamagnetic, paramagnetic, or [ferromag…