Question

Question #4730f

Answer 1

Magnetic force (or any other force) may be measured using a torsion balance, which is a sensitive device to measure force.
Coulomb, himself used a torsion balance to discover the Coulomb's law and inverse square law of forces between magnetic poles.

Now, the magnetic force a magnetic field `B` exerts on a charge `q` moving with velocity `v` making an angle `theta` with the field is given by the Lorentz force formula,

`F = qvBSin theta`

This gives an expression to calculate the magnetic force on a charged particle in a magnetic field.

Moreover, from the Coulomb's law of magnetic interations, the force of attraction (or repulsion) between two magnetic poles of pole strengths `q""_m1` and `q""_m2"` respectively separated by a distance `r` is given by, (in vacuum)

`F = (mu""_0*q""_m1q""_m2)/(4pir^2)`

where `mu""_0` is the permeability of free space. The force acts along the line joining the magnetic poles.