A copper bar of length h and electric resistance R slides with negligible friction on metal rails that have negligible electric
resistance (Figure 23.84). The rails are connected on the right with a wire of negligible electric resistance, and a magnetic
compass is placed under this wire (the diagram is a top view). The compass needle deflects to the right of north, as shown
on the diagram
Throughout this region there is a uniform magnetic field B pointing out of the page, produced by large coils that are not
shown. This magnetic field is increasing with time, and the magnitude is , where B0 and b are constants, and t
is the time in seconds. You slide the copper bar to the right and at time t = 0 you release the bar when it is a distance x
from the right end of the apparatus. At that instant the bar is moving to the right with a speed v.
(a) Calculate the magnitude of the initial current I in this circuit.
(b) Calculate the magnitude of the net force on the bar just after you release it.
(c) Will the bar speed up, slow down, or slide at a constant speed? Explain briefly.