# Earths Magnetic Flux

1. Apr 11, 2009

### muffintop

1. At a certain location, the Earth's magnetic field has a magnitude of 5.6x10-5 T and points in a direction that is 72 degrees below the horizontal. FInd the magnitude of the magnetic flux through the top of a desk at this location that measures 110 cm by 57 cm.

2. I used the formula $$\Phi$$ = BA cos $$\theta$$

3. The attempt at a solution
[tex]\Phi[/thex] = 5.6x10-5 x 1.10m x .57m x cos 72
=1.1e-5 Wb and it's wrong

2. Apr 11, 2009

### LowlyPion

Welcome to PF.

Is the desk top a vertical surface or a horizontal one?

http://hyperphysics.phy-astr.gsu.edu/Hbase/magnetic/fluxmg.html

3. Apr 11, 2009

### muffintop

Horizontal. and since the I'm looking for the magnetic flux, it should be perpendicular to the area so I use sine instead of cosine. What a stupid mistake haha, thank you for your help!