Hello.

Most of the time, the branch one takes in BTech is not based on his/her interest, rather on the placement scenarios of the college, cut-offs and parents/teacher advice. Student may realize his/her genuine interest after getting admitted in the college, which is totally fine.

In many colleges, there is an option to change the branch after first year based on the academic performance. So you can perform better in the first year and take the branch you want. If that is not possible, student can change the branch after 4 years while going to pursue MTech.

After investing 4 years in a branch, changing branch is a big decision. You should take into account some factors. Are you genuinely interested in that branch? Do you have required background knowledge in that branch? What are the future scopes?

If you are completely ready then you have to give an attempt to GATE in the specific stream that you are will to do in Masters.

Hope this is helpful.

Good luck.