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A uniform magnetic field lies exactly in the plane of a flat wire loop. What is the magnetic flux through the loop?
AIt is maximum
BIt is halved
CIt is zero
DIt is doubled
Answer & Solution
Correct answer: C. It is zero
1. Magnetic flux counts the part of the field that actually passes through the enclosed area.
2. A field lying in the plane of the loop is parallel to the surface.
3. A field parallel to the surface does not pass through it at all.
4. Only the component perpendicular to the surface contributes to the flux.
5. Here that perpendicular component is zero, so the flux is zero even though the field is not.
6. Calling the flux a maximum mixes up the parallel case with the perpendicular case, which is the trap.
_Source: Siyavula Physical Sciences Grade 11 (Everything Science, CC BY 4.0), Chapter 10: Electromagnetism_
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