A bar magnet is suspended from the free end of a helical spring, as illustrated in the figure below.
One pole of the magnet is situated in a coil of wire. The coil is connected in series with a switch and a resistor. The switch is open. The magnet is displaced vertically and then released. As the magnet passes through its rest position, a timer is started. The variation with time 
of the vertical displacement 
of the magnet from its rest position is shown in the graph below.
At time 
, the switch is closed, state, with a reason, whether the damping after time is light, critical or heavy.
