However, based on the popularity and positive reviews, the following are some of the best YouTube channels for physics, chemistry, and biology for Class 12 students:

Best YouTube Channels for Physics:

1. Physics Wallah - This channel is run by Alakh Pandey, who is a renowned Physics teacher. It has a vast collection of physics lectures in Hindi, which is beneficial for Indian students.

2. Khan Academy - It is one of the most popular educational channels on YouTube that provides free online courses in various subjects, including physics. The channel covers various topics and concepts of physics, from classical mechanics to quantum mechanics.

3. Veritasium - This channel is run by Derek Muller, who is a physicist and science communicator. The channel provides informative and engaging videos on various topics related to physics.

Best YouTube Channels for Chemistry:

1. Chemistry by Sal Khan - It is a sub-channel of the Khan Academy that provides free online courses in chemistry. The channel covers various topics and concepts of chemistry, from basic to advanced levels.

2. The Organic Chemistry Tutor - This channel is run by a chemistry tutor who provides tutorials and problem-solving videos for various topics in chemistry. The videos are easy to understand and follow.

3. Tyler DeWitt - This channel is run by a chemistry teacher who provides engaging and informative videos on various topics in chemistry. The videos are designed to help students understand the concepts and solve problems.

Best YouTube Channels for Biology:

1. Biology by Khan Academy - It is a sub-channel of the Khan Academy that provides free online courses in biology. The channel covers various topics and concepts of biology, from basic to advanced levels.

2. Crash Course Biology - It is a popular educational channel on YouTube that provides animated videos on various topics in biology. The videos are engaging and designed to help students understand the concepts.

3. Bozeman Science - This channel is run by a biology teacher who provides informative videos on various topics in biology. The videos are easy to understand and follow, and they cover various topics and concepts of biology.

In conclusion, these are some of the best YouTube channels for physics, chemistry, and biology for Class 12 students. These channels provide informative, engaging, and easy-to-understand videos that can help students understand the concepts and solve problems.