Current carrying wire and Earth’s magnetic field directions

[Qaztgbe]

Homework Statement

A telephone cable at a place has 4 long straight horizontal wires carrying a current of 1 ampere in the same direction east to west. The Earth's magnetic field at the place is .39G, the angle of dip is 35°, and the magnetic declination is nearly zero. What are the resultant magnetic fields (magnitude and direction) at points 4cm below the cable?

Homework Equations

μI/2∏r

The Attempt at a Solution

Magnitude of the field due to the current carrying wires is 2x10^-5T
Components of the earth’s magnetic fields –
Along the horizontal is B_Hcos35° = 3.19x10^-5T
Along the vertical is B_Vsin35° = 2.24x10^-5T

According to the right hand rule the magnetic field above the wires should be going into the plane and below should be coming out. I can’t ‘visualise’ the directions of the Earth's magnetic field so I can’t go any further.


I have numerous questions like this one but I can never see the direction of the earth’s field when it has different angles of dip.

 

[grzz]

This diagram may help you.

 

[Qaztgbe]

Definitely helped. If only I could 'see' it for myself everytime I get one of these questions. Thanks.