The flow of current in a circular wire creates a magnetic field at its centre

The flow of current in a circular wire creates a magnetic field at its centre. How can existence of this field be detected? State the rule which helps to predict the direction of magnetic field.

The existence of this field can be detected by using a magnetic compass needle. The direction of magnetic field is predicted by using Maxwell’s right hand thumb rule.
It states that if you hold a current-carrying conductor in right hand, such that the thumb points in the direction of electric current, then the direction in which fingers encircle, gives the direction of magnetic field.