UNIT OF MAGNETIC POLE STRENGTH

The force between two point poles 𝐦₁ and 𝐦₂ held at a distance 𝐫 apart, in any medium is given by

F=m1×m24π⋅μ0⋅μr⋅r2N

If in the above relation we put

𝑚₁ = 𝑚₂ = 1   (say)
r = 1  m

𝜇ᵣ = 1   (say in vaccum)
𝜇₀ = 4𝜋⨯ 10⁻⁷   H/m

then

F=1×14π(4π×10−7)1×1=116π2×10−7

From the above, we may derive the definition of a unit pole as that pole which when placed one meter away in free space (vacuum) from an equal and similar pole experiences repulsive force of
116π2×10−7  newtons    or   14πμ0  newtons.

This unit of pole strength is called Weber.