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Question #42922
The Question
A very large, isolated, thin non-conducting sheet has an initial area at temperature and carries a uniformly distributed total positive charge . A point particle of mass and positive charge is projected from a point near the sheet with an initial speed at an angle () with the normal to the sheet. The maximum perpendicular distance the particle travels from its projection point before turning back is . The sheet is then uniformly heated to a temperature . The coefficient of linear thermal expansion of the sheet material is . If the same particle is projected again from the same point with the same initial velocity, what is the new maximum perpendicular distance it reaches? (Assume , neglect gravity and edge effects).
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
Field due to Infinite Sheet|Variation of Density with Temperature|Conservative Force Field
Why This Question Is Tricky
Common Mistakes
This question tests the student's ability to couple thermal expansion with electrostatics, specifically targeting the misconception that surface charge density () is an invariant property of a charged sheet.
Students often incorrectly assume the electric field remains constant during heating (leading to option D).
Furthermore, by projecting the particle at an angle, the problem verifies the understanding of conservative force fields; the work done depends only on the normal displacement, isolating the normal kinetic energy component.
The correct approach requires recognizing that for an isolated sheet, total charge is conserved, so thermal area expansion () decreases , thereby weakening the electric field and increasing the stopping distance.
Quick Facts About This Question
Question Information
| Subject | Physics |
| Chapter | Electric Charges and Fields - Class 12 |
| Concept | Field due to Infinite Sheet |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |