You are Mohit/Minakshi of Class XII-C and a member of the school editorial board. Your school recently organised a science exhibition wherein the students showcased their science projects and models. Write a comprehensive report of the event to be published in the school newsletter. You may use the following cues along with your own ideas to compose the report.


A battery of emf \( E \) and internal resistance \( r \) is connected to a rheostat. When a current of 2A is drawn from the battery, the potential difference across the rheostat is 5V. The potential difference becomes 4V when a current of 4A is drawn from the battery. Calculate the value of \( E \) and \( r \).