Grounded-sphere image-charge solution
For a charge q at r₀ outside a grounded conducting sphere of radius a centered at the origin, an image q′=−qa/|r₀| at r′=a²r₀/|r₀|² gives the exterior potential q/(4πε₀|r−r₀|)+q′/(4πε₀|r−r′|).
Key knowledge
For a charge q at r₀ outside a grounded conducting sphere of radius a centered at the origin, an image q′=−qa/|r₀| at r′=a²r₀/|r₀|² gives the exterior potential q/(4πε₀|r−r₀|)+q′/(4πε₀|r−r′|). It vanishes at the sphere and infinity and satisfies the exterior source equation, so uniqueness establishes the solution.
Values and equations
q′=−qa/|r₀|; r′=a²r₀/|r₀|²; φ=q/(4πε₀|r−r₀|)+q′/(4πε₀|r−r′|)
- q,q′
- Source and image charges C
- a,r,r₀,r′
- Radius and positions m
- φ
- Exterior potential V
- ε₀
- Vacuum permittivity F m⁻¹
Conditions and scope
- |r₀|>a>0, vacuum, static isolated source and a grounded perfect conductor.
- The image is a computational source inside the excluded sphere, not an actual point charge in the metal; an isolated neutral sphere has different boundary data.
Sources · 1
References
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Evidence and review
Classical Electromagnetism (2014): Dirichlet Green's function for spherical surface: Equations 272–279: spherical exterior image Green function; point-source potential obtained by inserting a delta source.
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Entry details
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