Where is the file when I upload it?

[Anna]

I'm building an app, using RoR and activeAdmin, where the user can upload a file. I have asemantic_for_form which contains this:<%= f.input :uploaded_data, :as => :file %> and a method which is in charge to read the file uploaded by the user. My question is: where this file is upload? where the program stores it?

Thanks!