If a circular coil has current flowing in a clockwise direction, which way does the magnetic field point?

The right-hand thumb rule states that if a current-carrying conductor is imagined to be held in the right hand such that the thumb points in direction of the current, then curled fingers of the hand indicate the direction of the magnetic field.

Therefore, according to the right-hand thumb rule, the magnetic lines of force at the centre of the coil will be Turning inward along the coil's axis when the current passes through the circular coil in a clockwise direction.