The thumb sticking out gives the
direction of m (and A)
When this loop is placed in a uniform magnetic field B, the force F on
it is:  F = 0
And the torque on it is,
t = m × B
In a moving coil galvanometer, this torque is balanced by a counter-
torque due to a spring, yielding
kf = NI AB
where f  is the equilibrium deflection and k the torsion constant of
the spring 11 A moving coil galvanometer can be converted into a ammeter by
introducing a shunt resistance rs, of small value in parallel It can be
converted into a voltmeter by introducing a resistance of a large value
in series