A PhD in physics can potentially qualify an individual to teach engineering courses at a university, but this largely depends on specific circumstances and the nature of the courses. While there are instances of physics PhDs teaching engineering classes, particularly in areas where physics and engineering overlap, such as accelerator science or optics, it is not a blanket rule. The ability to teach engineering courses may also depend on the demand for lecturers, the specific subject matter, and the policies of the university. In cases where a physics department offers an engineering physics degree, physics faculty with relevant expertise may be able to teach engineering courses, especially if the university lacks a dedicated engineering school. Ultimately, competition and departmental politics play significant roles in determining who teaches which courses, with flexibility and demand being key factors for success in securing teaching positions outside one's primary field.