(A) : A moving charge is a source of magnetic field.
(R) : A current element is a source of magnetic field .

Options

A. Both 'A' and 'R' are true and 'R' is the correct explanation of 'A'.
B. Both 'A' and 'R' are true and 'R' is not the correct explanation of 'A'
C. 'A' is true and 'R' is false
D. 'A' is false and 'R' is false

Answer

To solve the question, we need to evaluate the two statements provided:

**Assertion (A): A moving charge is a source of magnetic field.**
**Reason (R): A current element is a source of magnetic field.**

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- A moving charge generates a magnetic field. This can be understood by considering a charge \( q \) moving with a velocity \( v \).
- According to electromagnetic theory, a moving charge creates a magnetic field around it. The magnetic field \( B \) produced by a moving charge can be described using the Biot-Savart Law.

2. **Understanding the Reason (R)**:
- A current element is defined as a small segment of current-carrying conductor. If we have a wire segment of length \( dL \) carrying current \( i \), this small segment can be treated as a current element.
- The magnetic field produced by this current element can be calculated using the Biot-Savart Law, which states that the magnetic field \( dB \) at a point in space due to a current element is proportional to the current and the length of the element.

3. **Linking Assertion and Reason**:
- The assertion states that a moving charge is a source of magnetic field, which is true. A moving charge constitutes a current, and thus, it produces a magnetic field.
- The reason states that a current element is also a source of magnetic field, which is also true. A current element generates a magnetic field around it.

4. **Conclusion**:
- Both statements are true. However, the reason (R) does not directly explain the assertion (A). The assertion is about a moving charge, while the reason discusses a current element, which is a different concept.
- Therefore, we conclude that both A and R are true statements, but R is not the correct explanation of A.

### Final Answer:
Both A and R are true, but R is not the correct explanation of A.

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