A current flow along the length of an infinitely long, straight thin-walled pipe . Then:

Options

A. the magnetic field at all points inside the pipe is same , but not zero
B. the magnetic field at any point inside the pipe is zero
C. the magnetic field is zero only on the axis of the pipe
D. the magnetic field is different at different points inside the pipe

Answer

To solve the problem of determining the magnetic field inside an infinitely long, straight thin-walled pipe carrying a current, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Setup**:
- We have an infinitely long, straight thin-walled pipe. The current flows along the length of the pipe, which means it flows on the surface of the pipe.

2. **Current Distribution**:
- Since the pipe is thin-walled, the current will only flow along the circumference of the pipe. There is no current flowing through the hollow center of the pipe.

3. **Applying Ampere's Law**:
- To find the magnetic field inside the pipe, we can use Ampere's Law, which states:
\[ \oint \mathbf{B} \cdot d\mathbf{L} = \mu_0 I_{\text{enc}} \]
- Here, \(I_{\text{enc}}\) is the current enclosed by the path we choose for our integration.

4. **Choosing an Amperian Loop**:
- We can choose a cylindrical Amperian loop of radius \(r\) that is entirely inside the pipe (i.e., \(r < R\), where \(R\) is the radius of the pipe).
- Since there is no current flowing through this loop (the current is only on the surface), we have:
\[ I_{\text{enc}} = 0 \]

5. **Calculating the Magnetic Field**:
- Substituting \(I_{\text{enc}} = 0\) into Ampere's Law gives:
\[ \oint \mathbf{B} \cdot d\mathbf{L} = \mu_0 \cdot 0 = 0 \]
- This implies that the magnetic field \(B\) inside the pipe is zero.

6. **Conclusion**:
- Therefore, the magnetic field at any point inside the pipe is zero.

### Final Answer:
The magnetic field at any point inside the pipe is zero.