A coil is rotated at a constant frequency f f\,f in a uniform magnetic field. The magnetic flux linking the coil is zero at time t1 t_1\,t1 and the induced electromotive force (emf) in the coil is zero at time t2t_2t2.
What is the smallest positive value of t1−t2t_1 - t_2t1−t2?
000
18f\frac{1}{8f}8f1
14f\frac{1}{4f}4f1
12f\frac{1}{2f}2f1