Yes, you can take the Electrical Engineering optional subject exam even if you are currently pursuing a Master's degree in a different field. The UPSC (Union Public Service Commission) allows candidates to choose their optional subjects based on their educational background and interest. Here's a detailed explanation of the process:

1. Eligibility Criteria:
- To appear for the UPSC Civil Services Examination, candidates must have a Bachelor's degree in any discipline from a recognized university.
- There are no specific restrictions on the choice of optional subjects based on the candidate's current field of study.

2. Choosing the Optional Subject:
- The UPSC offers a wide range of optional subjects, including Electrical Engineering.
- You can choose Electrical Engineering as your optional subject if you have a background or strong interest in the field, regardless of your current Master's degree.

3. Exam Pattern:
- The UPSC Civil Services Examination consists of three stages: the Preliminary Examination, the Main Examination, and the Personality Test (Interview).
- In the Main Examination, candidates are required to choose one optional subject from a list of subjects provided by the UPSC.
- The optional subject carries a total of 500 marks out of the 1750 marks for the Main Examination.

4. Preparation:
- Since your current Master's degree is in a different field, you may need to put in extra effort to prepare for the Electrical Engineering optional subject exam.
- Start by familiarizing yourself with the syllabus and exam pattern for Electrical Engineering.
- Gather relevant study materials, including textbooks, reference books, and previous years' question papers.
- It is advisable to join a coaching institute or online platforms like EduRev, which provide comprehensive study materials and guidance for UPSC optional subjects.

5. Time Management:
- Balancing your Master's degree with the preparation for the Electrical Engineering optional subject exam will require effective time management.
- Create a study schedule that allocates dedicated time for both your Master's degree coursework and UPSC exam preparation.
- Make use of weekends and holidays to focus on your optional subject preparation.

In conclusion, you are eligible to take the Electrical Engineering optional subject exam for the UPSC Civil Services Examination, irrespective of your current Master's degree. With proper planning, preparation, and time management, you can successfully appear for the exam and enhance your chances of securing a good rank.