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Question #89433
The Question
A semi-infinite distributed capacitive network is constructed along the -axis from to . The network is filled with a non-uniform dielectric material. For any small segment of length at position , the series capacitance is given by and the shunt capacitance to ground is , where and are geometric constants. The dielectric constants vary spatially as and , where and are positive dimensionless constants. Given the geometric relation , and defining a characteristic capacitance , what is the exact equivalent capacitance of the entire network as seen from the input terminal at ?
Options
- A.
- B.
- C.
- D.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Variable_Constraint
Develop pure symbolic logic skills by mastering algebraic constraints without relying on numerical data.
Concepts Behind This Question
Infinite Series Capacitance|Potential vs Field Relationship|Non-Uniform Dielectric Filling
Why This Question Is Tricky
Examiner Levers
Dimensional Analysis
Tests if the student verifies units/dimensions before selecting.
Difficulty Boost : +2Common Mistakes
This question tests the student's ability to transition from discrete, uniform infinite ladder circuits to a continuous, non-uniform field-theory model.
The primary trap lies in misapplying the standard characteristic capacitance formula for uniform distributed lines ().
Students who rely on rote memorization will locally evaluate this formula at and incorrectly choose .
The rigorous approach requires establishing a differential recurrence relation (charge conservation) that accounts for the spatial variation of the dielectric constant, leading to an Euler-Cauchy differential equation.
This highlights the danger of ignoring spatial gradients in distributed parameters and forces a fundamental derivation from electrostatic principles.
Quick Facts About This Question
Question Information
| Subject | Physics |
| Chapter | Electrostatic Potential and Capacitance - Class 12 |
| Concept | Infinite Series Capacitance |
| Difficulty | 5 |
| Cognitive Load | 6 |
| Target Solve Time | 140 sec |
| Access | Free |