Correct Option
The correct option is 1 and 4 only.
Explanation
A straight conductor carrying an electric current generates a magnetic field in its surrounding space. The pattern of this magnetic field is circular, and its direction is determined by the Right-Hand Thumb Rule. The magnitude of the field depends on the strength of the current and the distance from the conductor.
Statement-wise Analysis
- Statement 1 is Correct: The strength of the magnetic field ($B$) produced by a current-carrying conductor is directly proportional to the magnitude of the current ($I$) flowing through it ($B \propto I$). Therefore, at a fixed point, increasing the current increases the magnetic field strength.
- Statement 2 is Incorrect: The magnetic field strength is inversely proportional to the distance ($r$) from the conductor ($B \propto \frac{1}{r}$). As one moves further away from the wire, the field strength decreases; it does not remain constant.
- Statement 3 is Incorrect: Magnetic field lines around a straight conductor do not emerge radially like electric field lines from a point charge. Instead, they form closed loops.
- Statement 4 is Correct: The magnetic field lines form concentric circles centered on the wire. These circles lie in a plane perpendicular to the length of the conductor.
Key Takeaway: The magnetic field around a straight current-carrying wire consists of concentric circles. Its strength is directly proportional to the current and inversely proportional to the distance from the wire ($B \propto \frac{I}{r}$).