Practical marks in CBSE Class 10 are calculated based on the performance of students in the practical examinations conducted for subjects like Science and Computer Applications. These practical examinations are designed to assess the practical skills, understanding, and application of concepts by the students.

The practical marks are calculated using a specific marking scheme provided by CBSE. Here is a detailed explanation of how practical marks are calculated in CBSE Class 10:

1. Practical Examination: Students are required to perform experiments or practical tasks in a controlled environment under the supervision of their teachers. The practical examination is conducted to assess the practical skills and understanding of concepts.

2. Evaluation Criteria: The practical examination is evaluated based on specific criteria set by the CBSE. The criteria may include parameters like accuracy, neatness, presentation, understanding of the experiment, skill in handling apparatus, observation, interpretation of results, etc.

3. Lab Manual: Students are provided with a lab manual which contains a list of experiments, procedures, and observations. The lab manual serves as a guide for students to perform the experiments accurately and document their observations.

4. Practical File: Students are required to maintain a practical file where they record their observations, calculations, and other relevant information related to the experiments. The practical file is an important component in assessing the practical marks.

5. Viva Voce: In addition to the practical examination, students may also be assessed through a viva voce, where they are asked questions related to the experiment, theory behind it, and its applications. The viva voce helps in evaluating the depth of understanding and conceptual clarity of the students.

6. Marking Scheme: CBSE provides a specific marking scheme for each experiment or practical task. The marking scheme includes the weightage assigned to different components such as observation, accuracy, calculations, presentation, etc. Teachers use this marking scheme to evaluate the practical examination and assign marks accordingly.

7. Total Marks: The total marks for practical examination vary from subject to subject. In Science, practical examination is usually conducted for 20 marks, while in Computer Applications it is conducted for 30 marks.

In conclusion, practical marks in CBSE Class 10 are calculated based on the performance of students in the practical examination conducted for respective subjects. The evaluation is done using specific criteria, including accuracy, neatness, presentation, understanding, and skill. The practical file and viva voce also contribute to the assessment process. CBSE provides a marking scheme that guides the evaluation process, and the total marks for practical examination vary from subject to subject.