Magnetic flux through a loop at two orientations

[superslow991]

Homework Statement

A circular loop of radius 0.10 m is rotating in a uniform external magnetic field of 0.20 T. Find the magnetic flux through the loop due to the external field when the plane of the loop and the magnetic field vector are
(a) parallel.
(b) perpendicular.

Homework Equations

BAcos(theta)

The Attempt at a Solution

i know the answers for this problem but I am having trouble with the direction of the field and area and also the angle between them
For part a- I know its BAcos(90) but why is the angle 90 degrees? I was under the impression if the field and the loop are parrallel the angle should be 0?

For part b- Same thing BAcos(0) i thought the angle was suppose to be 90 degrees if they are perpendicular?

[Mentor note: Thread title adjusted to make it descriptive of the problem]

 

[TSny]

Consult your textbook or notes to see how the angle θ is defined in the expression BAcosθ.

 

[superslow991]

Homework Statement

** EDITED ORIGINALPOST
A circular loop of radius 0.10 m is rotating in a uniform external magnetic field of 0.20 T. Find the magnetic flux through the loop due to the external field when the plane of the loop and the magnetic field vector are
(a) parallel.

Homework Equations

BAcos(theta)

The Attempt at a Solution

So i know if the field and the loop are parallel the angle is 0 so i tried

flux = (0.2)*(0.03141)*cos(0) = 0.06282 but the answer is suppose to be 0.

This would be true if the if i did (0.2)*(0.03141)*cos(90) so I am not sure where I am at fault.

 

[TSny]

θ is not the angle between the plane of the loop and B. It's the angle between the normal direction of the loop and B.

 

[superslow991]

θ is not the angle between the plane of the loop and B. It's the angle between the normal direction of the loop and B.

Thanks, is there anyway i can read up on this?

 

[gneill]

Thanks, is there anyway i can read up on this?

Of course. The information is readily available if you have a web browser.

Do a web search on the terms of interest, say: "magnetic flux loop angle".