A clock face rule is a mnemonic that is used to determine the magnetic polarity of a circular coil that carries current.
The clock face rule states that if you look at one face of the coil, and the current appears to be flowing clockwise, that face is a south pole.
And conversely, if the current appears to be flowing counterclockwise, that face is a north pole.
Imagine the coil as a clock face by visualizing the circular coil with the current flowing around it.
If the current flows in the same direction as the hands of a clock "clockwise", the face you are looking at is a south pole.
If the current flows in the opposite direction of the hands of a clock "counterclockwise", the face you are looking at is a north pole.
This rule is also useful for determining the magnetic polarity of electromagnets or any circular loop of wire carrying current.
Here, the clock rule says that “When an observer, looking at the face of the coil, finds the current to be flowing in the anti-clockwise direction, here the face of the coil will behave like a North Pole, whereas if the current is in the clockwise direction, the face of the coil will behave like a South Pole.”