Magnetic Field Direction Rule

The direction of the magnetic field at the centre of a current-carrying circular loop is determined using the Right-hand rule, specifically by curling the fingers of the right hand in the direction of the current flow around the loop.

Applying the Right-Hand Rule

• Grip the loop: Imagine gripping the circular loop with your right hand.
• Curl fingers: Curl your fingers in the same direction as the electric current is flowing in the loop.
• Thumb direction: Your extended thumb will point in the direction of the magnetic field at the centre of the loop.

This rule directly links the direction of current in the loop to the resulting magnetic field direction inside the loop.

Why Other Rules Are Less Suitable

• Fleming's left-hand rule: This rule is primarily used to determine the direction of force on a current-carrying conductor placed in a magnetic field (motor principle), not the field direction itself.
• Left-hand thumb rule: Generally associated with left-hand rules for force direction.
• Right-hand palm rule: While related, the specific method described in option B (curling fingers along current) is the standard and clearest way to apply the right-hand rule to loops for field direction.

Therefore, the Right-hand rule (curling fingers along current) is the correct method.