Suppose this page is perpendicular to a uniform magnetic field and the magnetic flux through it is 5 Wb. If the page is turned by 30 $\degree$around an edge the flux through it will be:
A) 2.5 Wb
B) 4.3 Wb
C) 5 Wb
D) 5.8 Wb
E) 10 Wb

Question

Quizplus · Accepted Answer

When the page is turned by 30 degrees, the magnetic flux through it will be reduced because the magnetic field lines are now passing through it at an angle rather than perpendicular. 
The new flux can be calculated using the formula: 
new flux = old flux x cos(angle of rotation) 
new flux = 5 Wb x cos(30 degrees) 
new flux = 4.33 Wb (rounded to two decimal places)

Therefore, the best choice is B, 4.3 Wb.

Suppose This Page Is Perpendicular to a Uniform Magnetic Field °\degree°

Suppose This Page Is Perpendicular to a Uniform Magnetic Field $\degree$