  Using molecular dynamics simulations, we study particle-transport in a system
of interacting colloidal particles on a ring, where the system is driven by a
time-dependent external potential, moving along the ring. We consider two
driving protocols: (i) the external potential barrier moves with a uniform
velocity $v$ along the ring, and (ii) it moves in discrete jumps with
jump-length $l$ and waiting time $\tau$ with an effective velocity $v=l/\tau$.
The time-averaged (dc) particle current, which always remains positive in case
(i), interestingly reverses its direction in case (ii) upon tuning the
particle-number density $\rho_0$ and the effective barrier velocity $v$. We
also find a scaling form for the current in terms of number density, barrier
velocity, barrier height and temperature of the system.
