Question

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 the axis. Through what angle must the door rotate so that the magnetic flux that passes through it decreases from its maximum value to 1/4 of its maximum value?

Answer 1

75.5degrees

Step-by-step explanation:

Magnitude of magnetic flux= BA

If rotated through an angle= BAcos theta

= (0.25)BA=BAcos theta

= costheta= 0.25

= theta= cos^-1 0.25

=75.5degrees