A probabilistic method is used to obtain an exact analytic expression
for the zero-temperature and zero-frequency limit of the hysteresis lo
op in a one-dimensional Ising model with an arbitrary continuous distr
ibution of quenched random fields. The solution illustrates important
differences between bounded and unbounded probability distributions of
the quenched fields. The significance of this result is discussed in
the wider context of the Barkhausen noise observed in experiments as w
ell as numerical simulations of three-dimensional systems.