The marks needed to pass the external exam in the event that a student receives no marks on the internal exam will be determined by the institution's overall pass criterion.

For instance, if the passing score for a topic is 40% overall and the total marks are divided between internal and external exams (for instance, 30% internal and 70% external):

40% of the possible points in the external exam must be earned by the student if their internal marks are zero.

Assume this:

100 total points
30 marks for the internal test
70 points for the external exam
40% is the passing percentage (40 out of 100).

If you have obtained no marks in your internal exams, you might have to obtain higher marks than that in the external (final) exam in order to pass on the basis of your university rules. For example, if in your **Anna University**, you got 0 marks in your internal marks, you would have to get at least 63 out of 100 marks in the external exam in order to get the minimum grade that is normally an "E" grade. The internal marks normally make up as much as 20 percent of your total mark. So, the lack of internal marks makes it slightly challenging but not impossible to pass.

However, if you are studying from a different institution, then requirements might be other. It would be good to cross-check with your college or scan your exam instructions provided by the place for the right information.

Thankyou!