What to do when PhD advisor wants student to work on two disjoint projects? My PhD advisor wants me to work on two different problems during my PhD. One is the a problem of their suggestion and another is collaborative work with some company. Both the problems are disjoint. I have been given  the option, that if I want to work on one problem  then it should be the problem on for my advisor's collaborative research and I should leave the problem initially suggested. However, I don't want to give up my present problem as that sounds interesting to me and I have already worked for one year on it. When I told my advisor that I don't find the collaborative work interesting, it was suggested that I work on both the problems. However, I am finding it hard to work on two problems. Its like a dual PhD for me. I cannot say anything to my advisor as I'm told I have to work on the collaborative work as my stipend comes from it and else I should leave the PhD. My advisor also does not  advise me when I propose ideas about my previous research. Please suggest what should I do?
The most important line in your post seems to be one that you didn't give much weight to: "my stipend comes from [the collaborative project]". From my experience, this is a common situation, where the money for your stipend comes from a project you're not interested in pursuing.

Unfortunately, the only real alternative for you is to write your own grant proposal, which is a significant investment of time for both you and your advisor, and carries the not-so-minor risk that the grant won't be funded, which leaves you exactly where you started, with the added problem that there hasn't been much progress on the existing grant.

The second alternative is to leave the advisor and try to find someone else, but I would recommend against that for two reasons. Firstly, it's hard to find someone else with funding on a project you like. Secondly, the problem you're having now—the funded project is less interesting than the unfunded project—is one you'll likely face again in the future. Your advisor's approach of pursuing both projects is (again, from my experience) a typical way of dealing with this, and it will likely benefit you to have experience with this approach during your PhD years.

I recognize that it means extra work for you, and I don't really have much advice on that front. Try not to think of it as extra work, but rather as extra publications in different research areas. That helps minimize the sting.