Coil A is fixed horizontally on a workbench and is connected in series with a DC cell and a switch. Coil B is a closed, lightweight copper ring suspended horizontally by thin insulating threads directly above Coil A, sharing a common vertical axis.
The switch in the circuit of Coil A has been closed for a long time.
Describe and explain the direction and the duration of the magnetic force experienced by Coil B at the instant the switch is opened.