Rules to Determine the Direction of Magnetic Field

• Setup: Stretch the right hand so the thumb points along the direction of current I, and the fingers point toward the point of interest P.

• Result: The perpendicular drawn outward from the palm gives the direction of the magnetic field B at that point.
• Best used for: Quickly finding field direction at an off-axis point near a straight conductor.

• Setup: Grasp the straight conductor with the right hand such that the thumb points along the direction of current flow.

• Result: The direction in which the fingers curl around the conductor gives the direction of the magnetic field lines B.
• Best used for: Visualising circular/concentric field lines around a straight wire.

• Setup: Imagine a right-handed screw being driven along the direction of current flow.

• Result: The direction in which the screw's head must be rotated (to advance) gives the direction of the magnetic field.
• Best used for: Conceptual/theoretical problems and diagrams involving rotational field representation.

Think of twisting a jar lid or driving a screw into wood: the direction your hand pushes (forward, like current) determines the rotational direction your fingers/screwdriver turn (like the magnetic field looping around it). This is exactly the physical relationship Maxwell's Screw Rule captures.