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As shown in figure , a circular loop of wire has a radius R. A magnetic field is directed into the page ; its magnitude is given by B ( r , t ) = Ar²t² , where r is the distance to the center of the loop ( origin ) , and A is a constant . At time t , what is the magnitude of the emf induced in the loop ? [ 10 % ]
y хххххх х х х х х х Rxxx X X X X x xxxxxxx xxxxxxxxx x x x x x x x x x x xxxxxxxxxxxx X X X X X X X X Х Х Х Х Х x x x x x x x B xx XX Х

y хххххх х х х х х х Rxxx X X X X x xxxxxxx xxxxxxxxx x x x x x x x x x x xxxxxxxxxxxx X X X X X X X X Х Х Х Х Х x x x x x x x B xx XX Х