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Question #43440
The Question
An electron of mass (in ) and charge (in ) revolves counterclockwise in the -plane in a circular orbit of radius (in ) with a constant angular speed (in ) around the origin. A closed spherical surface of radius (in , where ) is centered at the origin. Let (in ) be the net magnetic flux through the entire surface , and (in ) be the magnitude of the magnetic flux through the upper hemisphere () of . Which of the following correctly represents and ? (Assume vacuum with permeability in )
Options
- A.
,
- B.
,
- C.
,
- D.
,
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Multi-Concept_Bridge
Master problems that require linking physics and math concepts to solve complex competitive questions.
Concepts Behind This Question
Gauss’s Law for Magnetism|Magnetic Dipole Moment of Revolving Electron|Variable Force Integration
Why This Question Is Tricky
Common Mistakes
This question tests the application of Gauss's Law for Magnetism and the integration of a non-uniform magnetic dipole field.
A common trap is assuming that a localized current loop behaves analogously to a net electric charge, leading students to incorrectly guess a non-zero total flux.
Furthermore, calculating the hemispherical flux forces students to correctly apply the dipole field formula in spherical coordinates and perform a surface integral.
Alternatively, astute students can use the divergence theorem to equate the hemispherical flux to the flux through the equatorial plane outside the loop, testing their transition from calculus-heavy brute force to conceptual physical intuition.
Quick Facts About This Question
Question Information
| Subject | Physics |
| Chapter | Magnetism and Matter - Class 12 |
| Concept | Gauss’s Law for Magnetism |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |