Chapter 21, Problem 35P

* A toy electric generator has a 20-tum circular coil with each turn of radius 1.8 cm. The coil resides in a 1.0-T magnitude $\stackrel{\to }{B}$ field It also has a lightbulb that lights if the potential difference across it is about 1 V. You start rotating the coil, which is initially perpendicular to the $\stackrel{\to }{B}$ field. (a) Determine the time interval needed for a $90°$ rotation that will produce an average induced emf of 1.0 V. (b) Use a proportion technique to show that the same emf can be produced if the time interval for one rotation is reduced to one-fourth while the radius of the coil is reduced by one-half.