Electric Dipole
An electric dipole consists of charges +q and -q separated by distance 2a. What is the electric field at a point on the axial line at distance r from the center (r >> a)?
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About This Question
- Subject
- physics
- Chapter
- electrostatics
- Topic
- electric dipole
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
2kp/r³
- Dipole Moment: Defined as p=q×2a.
- Exact Axial Field: E=4πϵ01(r2−a2)22pr.
- Approximation for Far Points: If r≫a, then a2 becomes negligible compared to r2.
- Simplify:
- E≈4πϵ01r42pr=4πϵ01r32p.
- Result: E=r32kp, where k is the Coulomb constant. Note that the field strength for a dipole drops much faster (1/r3) than for a single point charge (1/r2).
This medium difficulty physics question is from the chapter electrostatics, covering the topic of electric dipole. It appeared in the 2025 exam.
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