Question #4730f

1 Answer
May 30, 2015

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.