1, The magnetic flux is decreasing when the area is decreased. By Lenz's law to oppose the decrease the induced current produces a magnetic field into the page. Hence current flow in clockwise direction, the current flow from A to B. The end B is more positive than end A.
2. The induced e.m.f = change in magnetic flux /time taken. E = NBchange in area/time or E = NA change in B /time. Be flexible to calc the two cases.
3. The solenoid produce B of 1.5 mT. The formula B = u n I , where n is N/l of solenoid. There is flux in the solenoid flux = NBA. The 8 turn coil wound around the solenoid experinces the same change in B in the solenoid. So the change in flux = change in NBA , where the B changes from positive to negative direction based on the currents shown as P and Q on graph. P and Q shows the current changing direction and hence B change direction from positive to negative. The change in B = 2B. Hence the induced E= 2NBA/time taken. Note the gradient of I - t graph gives the E- t graph. Showing by formula: E = NAun(dI/dt) wehre N is 8 turns and dI/dt is constant.
