# Homework Help: Magnetic flux through a loop at two orientations

1. Apr 8, 2017

### superslow991

1. The problem statement, all variables and given/known data

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.

2. Relevant equations
BAcos(theta)

3. The attempt at a solution
i know the answers for this problem but im 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]

Last edited by a moderator: Apr 9, 2017
2. Apr 8, 2017

### TSny

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

3. Apr 9, 2017

4. Apr 9, 2017

### 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.

5. Apr 9, 2017

### superslow991

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

6. Apr 9, 2017

### Staff: Mentor

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".