Correct Option
The correct option is A is false but R is true.
Explanation
A current-carrying conductor produces a magnetic field in its vicinity. The pattern of this magnetic field depends on the shape of the conductor. The direction of the magnetic field lines is determined by the Right-Hand Thumb Rule (or Maxwell’s Corkscrew Rule).
Statement-wise Analysis
- Assertion (A): Incorrect
The magnetic field lines around a straight current-carrying wire are not straight lines parallel to the wire. Instead, they form concentric circles centered on the wire. These circles lie in a plane perpendicular to the length of the wire. The magnetic field is strongest near the wire and decreases as the distance from the wire increases.
- Reason (R): Correct
The direction of the magnetic field is directly dependent on the direction of the current flowing through the conductor. According to the Right-Hand Thumb Rule, if the direction of the current is reversed, the orientation of the magnetic field lines (clockwise vs. anti-clockwise) also reverses.
Key Takeaway: Magnetic field lines around a straight current-carrying conductor are concentric circles perpendicular to the conductor, and their direction reverses with the reversal of current.