PhysicsLAB AP Free Response Question
1999 C2 E&M

A uniform magnetic field B exists in a region of space defined by a circle of radius a = 0.60 m as shown below. 
 
 
The magnetic field is perpendicular to the page and increases at a constant rate of 0.40 T/s. A singular loop of wire of negligible resistance, and radius r = 0.90 m is connected to a light bulb with a resistance R = 5.0 Ω, and the assembly is placed concentrically around the region of magnetic field.
 
 (a) Determine the emf induced in the loop.

 (b) Determine the magnitude of the current in the circuit.  On the figure above, indicate the direction of the current in the loop at point O.

 (c) Determine the total energy dissipated in the light bulb during a 15 second interval.

The experiment is repeated with a loop of radius b = 0.40 m placed concentrically in the same magnetic field as before. 
 
 
The same light bulb is connected to the loop, and the magnetic field again increases out of the page at a rate of 0.40 T/s.  Neglect any direct effects of the field on the light bulb itself.
 
 (d) State whether the brightness of the bulb will be greater than, less than, or equal to the brightness of the bulb in part (a).  Justify your answer





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