A vertical straight conductor carries a current vertically upwards. A point P lies to the east of it at a small distance and another point Q lies to the west at the same distance. The magnetic field at P is

For upward direction current magnetic field will be anticlockwise, so on the eastern side it will be towards north; northern side it will be towards west and so on. Horizontal component of earth magnetic field is towards north, so on the eastern side they support each other and on the western side they oppose each other.