Lenz's Law states that an electromotive force (emf) is generated when there is a change in magnetic flux. Motional emf, on the other hand, can produce an emf without a change in flux. In physics problems, magnetic flux is defined as the product of the magnetic field strength, area, and the cosine of the angle between them. For most assignments, the flux will vary with time, requiring students to identify which variable (magnetic field, area, or angle) changes. Understanding these concepts is crucial for solving related problems effectively.