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**What is pole strength of a bar magnet? Is it the same as the dipole moment?**

We know that a bar magnet when placed in a magnetic field $B$ experiences a torque given by

$τ=M×B$ where M is the magnetic dipole moment

The moment of a couple with arm length d is given by $τ=d×F$

Equating the above expressions we can see that,

$Fdsinθ=MBsinθ$

$F=dM B$

Let us say,

pole strength, $q_{m}=dM $

On comparing the above expression to the force on a charge due to electric field E, $qE$, we can say,

with analogy from electrostatics,

**pole strength is the equivalent of electric charge. Pole strength is NOT the same as dipole moment.**