What is the expiation for cheating on exams, and is it necessary to inform the course professor, or is repentance sufficient?

Deceit is forbidden and blameworthy. A believer is not characterized by it, as the Prophet, peace and blessings be upon him, said: "Whoever deceives us is not of us," and his saying: "Whoever deceives is not of me." This includes deception in exams and other matters. The effect of deceit on a future job is removed by repentance, and the salary for the job is permissible if the required work is performed.