Dear student,
This completely depends on the college that whether it allows you to change your branch while taking admission through lateral entry in a particular college. Some colleges allow you to do so while some don't. So you need to check each college's rules to know which colleges to join so that you can choose your desired branch. However if you are really passionate about electrical engineering then you can appear for exams like jee mains and get into a branch of your choice in 1st year of b.tech.

Dear student,

Yes, you can change your branch in btech to electrical even if you are a civil engineering diploma holder. But for that, you must have to appear for a lateral entry test for that college. And then have to secure a rank in it. Then only your brand can be changed to electrical. And try to score a good rank in the lateral entry test so as to get the electrical branch.