I have passed class 12th from UP Board. Can I take admission in Diploma in Electrical Engineering?

Yes, the board is not a hurdle in taking the admission. The only thing is that you have to pass class 10th to take a Diploma course after class 10th, and there is a Diploma course after class 12th. You can also opt for that also, but you have to take Science in class 12th for that and at least 50 pe