Flux changes with area.

The wire on the right is pulled to the right for 5 seconds and then to the left for 5 seconds as shown.  What is the magnitude of the magnetic field passing through the wire rectangle.  You may pause the simulation and read coordinate values by click-dragging the mouse at any time. The meter displays the induced emf in millivolts.  Start.

You can also plot V(t).

NOTE:  The size of the wire changes when the plot is displayed.  This causes different readings in the two modes.