The rule that determines the direction of a magnetic field produced around a straight conductor carrying current is :

The direction of the magnetic field produced around a straight current-carrying conductor is determined by the Right-hand thumb rule, also known as the Right-hand grip rule. According to this rule, if you hold the conductor in your right hand with the thumb pointing in the direction of the electric current, the curled fingers indicate the direction of the magnetic field lines [1]. These field lines form concentric circles centered on the wire [1]. While Fleming's left-hand rule is used to find the direction of force on a conductor in a magnetic field and Fleming's right-hand rule is used for induced current, the Right-hand thumb rule specifically relates the current direction to the surrounding magnetic field orientation. Hund's rule is a principle in chemistry regarding electron configuration and is unrelated to electromagnetism.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 12: Magnetic Effects of Electric Current > 12.2.2 Right-Hand Thumb Rule > p. 199