You are Mr. Abhishek Sharma. You are planning to celebrate your parents’ 50th wedding anniversary in a grand manner. Draft a formal invitation card for your friends and relatives. Mention all necessary details.


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 \( r \).