How Does Earth's Magnetic Field Flux Change with Loop Orientation?

[goWlfpack]

Magnetic flux!

Homework Statement

Find the flux of Earth's magnetic field of magnitude 5.00 10-5 T through a square loop of area 40.0 cm2 for the following:
(a) when the field is perpendicular to the plane of the loop



(b) when the field makes a 20.0° angle with the normal to the plane of the loop

Homework Equations

flux = BA cos theta
where A is the area and B is the magnetic field

The Attempt at a Solution

on the first one i just multiplied 5e-5 by .4 and i got 2.0e-5... and it was wrong and i have NO idea why

the second one i just used the answer i got previously (obviously wrong) and multiplied it by cos of 20... red x
HELP!

 

[borgwal]

You have to convert cm^2 to m^2 in the correct way

 

[goWlfpack]

You have to convert cm^2 to m^2 in the correct way

the correct way? its not directly proportional?

 

[borgwal]

It's directly proportional, but not with the proportionality constant you think!

You seem to think that 40 cm^2 equals 0.4 m^2. That's not true!