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Question #42786
The Question
A parallel plate capacitor consists of two rectangular plates of length and width , separated by a distance . A dielectric slab of length , width , thickness , and dielectric constant is partially inserted a distance between the plates, parallel to the plates. A constant potential difference is maintained across the capacitor. The electric force pulling the slab into the capacitor is calculated from the system's parameters. If the maximum absolute errors in measuring the slab thickness and plate separation are and respectively, what is the maximum percentage error in the calculated value of ? (Assume , , , and are exact constants, and edge effects are negligible).
Options
- A.
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- D.
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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
Dielectric Slab Displacement|Symmetry and Virtual Work|Relative Error Propagation in Powers
Why This Question Is Tricky
Common Mistakes
The problem tests the student's ability to correctly apply the Principle of Virtual Work to find the force on a dielectric and then rigorously propagate measurement errors through a non-linear algebraic expression.
A common trap is failing to treat the effective plate separation as a composite variable dependent on both and .
Students often incorrectly assume (leading to ) or simply add the base relative errors (leading to ), ignoring the cross-dependence in the denominator .
Another trap is making a sign error during logarithmic differentiation, leading to the subtraction of error terms instead of adding their absolute values for the maximum possible error (leading to ).
Quick Facts About This Question
Question Information
| Subject | Physics |
| Chapter | Electrostatic Potential and Capacitance - Class 12 |
| Concept | Dielectric Slab Displacement |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |