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Question #43443
The Question
A closed electrical circuit consists of a capacitor of capacitance and two wire loops, Loop 1 and Loop 2, connected in series. The total self-inductance of the two loops is . Loop 1 is a small planar loop of area fixed at the origin in the -plane. Loop 2 is a wire bent into the shape of an open hemispherical dome of radius . The circular base of the dome has area . The center of this base is located at a distance from the origin along the -axis, where and . Loop 2 is forced to rotate about an axis parallel to the -axis passing through the center of its base, with a constant angular velocity . At , the circular base of Loop 2 is parallel to the -plane. Assume the resistance of the circuit is negligible and that at , the magnetic fluxes produced by the two loops reinforce each other. Let be the instantaneous charge on the capacitor, and define a constant . By applying Gauss's Law for Magnetism to determine the flux linkage, identify the correct differential equation governing .
Options
- A.
- B.
- C.
- D.
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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|Dot Product Geometry|L-C Circuit Analogy
Why This Question Is Tricky
Common Mistakes
This question tests the synthesis of Gauss's Law for Magnetism, dipole field geometry, and Faraday's Law in a time-varying circuit.
The primary trap lies in the time derivative of the flux linkage.
Students often incorrectly assume that the induced EMF in an LC circuit is simply , treating inductance as a constant.
Here, the rotation of the loop creates a time-varying mutual inductance .
By failing to apply the product rule to , students miss the term entirely, which acts as a parametric damping factor.
Additionally, the problem requires applying to simplify the flux integral over a complex hemispherical surface to a simple dot product over its circular base, and remembering the factor of 2 for mutual inductance in series-aiding coils.
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 |