|
|
|||||||||||||||||||
|
13. ssm
A standard door into a house
rotates about a vertical axis through one side, as defined by the door’s
hinges. A uniform magnetic field is parallel to the ground and perpendicular
to this axis. Through what angle must the door rotate so that the magnetic
flux that passes through it decreases from its maximum value to one-third of
its maximum value? |
|||||||||||||||||||
|
|
|||||||||||||||||||
|
On the left
we have the door at maximum magnetic flux.
On the right we have less. Magnetic flux is |
|||||||||||||||||||
|
|
|||||||||||||||||||
|
|
|||||||||||||||||||
|
Where q
must be angle between |
|||||||||||||||||||
|
|
|||||||||||||||||||
|
By inspection you can see that
φ = q ! so if we find q,
we are finding how far the door was rotated.
So we want magnetic flux to decrease by a
factor of 1/3. |
|||||||||||||||||||
|
|
|||||||||||||||||||
|
|
|||||||||||||||||||
|
|
|||||||||||||||||||
|
|
|||||||||||||||||||
|
Solve for q |
|||||||||||||||||||
|
|
|||||||||||||||||||
|
|
|||||||||||||||||||
|
|||||||||||||||||||
|
|
|||||||||||||||||||
|
|
|||||||||||||||||||
|
|||||||||||||||||||
|
|
