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Question #42653
The Question
A solid non-conducting sphere of mass , radius , and total positive charge is placed on a rough inclined plane that makes an angle with the horizontal. The incline slopes upwards to the right. The sphere has a non-uniform internal charge distribution such that its Effective Center of Charge (ECC) is located at a distance vertically below its Center of Mass (CM). A uniform horizontal electric field of magnitude is applied in the rightward direction. The incline is sufficiently rough to prevent slipping. If the sphere remains in both translational and rotational equilibrium, what is the required magnitude of the electric field ? (Take and )
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
Non-conducting Charged Sphere|Friction on Inclined Planes|Newton’s Third Law Pairing
Why This Question Is Tricky
Common Mistakes
This question tests the student's ability to distinguish between the Center of Mass (CM) and the Effective Center of Charge (ECC) in rigid body equilibrium.
A common trap is to treat the electrostatic force as acting at the CM, similar to gravity in a uniform field, which incorrectly yields zero electrostatic torque.
By placing the ECC vertically below the CM, the horizontal electric field generates a counter-clockwise torque that must be balanced by the clockwise torque from static friction.
Students who ignore the ECC displacement will incorrectly conclude that friction is zero (from torque equilibrium) and solve only the translational force balance, leading to the erroneous answer of 3Mg/4Q.
Quick Facts About This Question
Question Information
| Subject | Physics |
| Chapter | Electric Charges and Fields - Class 12 |
| Concept | Non-conducting Charged Sphere |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |