The magnetic field in a straight current carrying conductor wire is:

Options

A. Upward to downward
B. Downward to upward
C. All around
D. In a circular path

Answer

To determine the magnetic field around a straight current-carrying conductor, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Direction of Current**:
- Consider a straight conductor carrying current \( I \). For this example, let's assume the current is flowing upward.

2. **Apply the Right-Hand Thumb Rule**:
- The right-hand thumb rule states that if you point your thumb in the direction of the current (upward in this case), your curled fingers will indicate the direction of the magnetic field lines around the conductor.

3. **Visualize the Magnetic Field**:
- As you curl your fingers around the wire, you will notice that the magnetic field lines form concentric circles around the wire. The direction of the magnetic field will be perpendicular to the direction of the current.

4. **Determine the Direction of Magnetic Field at Various Points**:
- If you want to find the direction of the magnetic field at different points around the wire:
- Above the wire (where your fingers curl downwards), the magnetic field points into the page (represented by a cross).
- Below the wire (where your fingers curl upwards), the magnetic field points out of the page (represented by a dot).

5. **Conclusion**:
- The magnetic field around a straight current-carrying conductor is circular and its direction can be determined using the right-hand thumb rule. The field lines are concentric circles centered on the wire.

### Final Answer:
The magnetic field in a straight current-carrying conductor wire is in a circular path around the wire, with the direction determined by the right-hand thumb rule.

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