Physics 21 Fall 2007 Solution to HW-16 29-6 A coil of radius r , containing N turns, is placed in a uniform magnetic field whose magnitude varies with time according to B=C _0 t + C _1 t ^4. The coil is connected to a resistor R , and its plane is perpendicular to the magnetic field. You can ignore the resistance of the coil. (A) Find the magnitude of the induced emf in the coil as a function of time. (B) What is the current in the resistor at time t_0? 29-9 Shrinking Loop A circular loop of flexible iron wire has an initial circumference of C (0), but its circumference is decreasing at a constant rate dC/dt due to a tangential pull on the wire. The loop is in a constant, uniform magnetic field oriented perpendi-cular to the plane of the loop of magnitude B . (A) Find the emf induced in the loop at the time t = 9.0 s. (B) Find the direction of the induced current in the loop, as viewed looking along the direction of the magnetic field 29-10 A rectangle measuring 30.0 cm by 40.0 cm is located inside
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