The duration of each paper in the Electrical Engineering optional subject exam varies depending on the specific examination conducted by UPSC (Union Public Service Commission). However, typically, each paper in the Electrical Engineering optional subject exam has a duration of 3 hours.

Here is a breakdown of the duration and structure of each paper:

1. Paper I:
- Duration: 3 hours
- This paper focuses on the fundamentals of electrical engineering, including circuit theory, electrical machines, power systems, and measurements.
- It consists of a total of 8 questions, out of which candidates are required to answer 5 questions.
- The questions are designed to assess the candidate's understanding of the core concepts and their ability to apply them in solving problems.

2. Paper II:
- Duration: 3 hours
- This paper covers advanced topics in electrical engineering, such as control systems, communication systems, and digital electronics.
- It consists of a total of 8 questions, out of which candidates are required to answer 5 questions.
- The questions in this paper are aimed at evaluating the candidate's knowledge of advanced concepts and their ability to analyze and solve complex problems related to electrical engineering.

Overall, each paper in the Electrical Engineering optional subject exam has a duration of 3 hours, and the questions are designed to assess the candidate's knowledge, understanding, and problem-solving skills in various areas of electrical engineering. It is important for candidates to manage their time effectively during the exam to ensure they can answer the required number of questions within the given duration.