[nihar]

It depends on what your contract says... I work for a firm that clearly states that whatever you do, if it involves their equipment, resources, or time, or knowledge gained while working with them, they have IP rights at that point. That being said, some companies allow you to do stuff on your own, e.g. work for a different client / project outside your billable hours, and they don't have rights to those products (as long as you're clearly showing that you're not using shared resources).