A uniform magnetic field exists in a square of side 2a (as shown in figure). A square loop of side a enters the field along a diagonal and leave it at a constant speed. Draw the curve between induced emf e and distance along the diagonal, say xo.

The graph is to be drawn qualitatively       As shown, for 0 ≤ x ≤ aφ=Bx2 e=-dφdt=-2B.dxdt=-2BxvAt  x = 0, e = 0At   x = a/2, e=-BavAs, x→a but x≠a,e≈-2BavAs,  x=a, e=0 as φ=constantDistance along diagonal When the loop reaches completely inside the field, it starts coming out of the field after some moment. When the loop is coming out, x1 should be selected carefully, for whichφ=Ba-x12e=-dφdt=-2Ba-x1.v=2Ba-x1vAt  x1=0, e =2Bavx1=a, e=0Thus, before the loop enters the field completely, e = - 2Bav. When the loop is completely inside the field, e = 0 (φ = constant). As the loop starts coming out of the field (e = -2Bav). Option (4) is correct.