A current is flowing in an electricity line towards the north, the direction of the magnetic field at a point which is just below the line is :

 A current is flowing in an electricity line towards the north, the direction of the magnetic field at a point which is just below the line is towards west 

Apply Right hand-thumb rule
Place your palm on the current-carrying conductor and surrounds the conductor with your fingers and your thumb should be in the direction of the current flowing
Now at any point, the magnetic field lines' direction will be the same as the direction of your fingertips.