A random sample of conventional references (incorrectly) assuming a point to sphere force calculation is approximated as a point to point calculation
Xabier Cid Vidal (2021, June 27), Coulomb’s law, Large Hadron Collider web site, https://www.lhc-closer.es/taking_a_closer_look_at_lhc/0.coulomb_law
Glenn Elert, (2021, June, 27), The Physics Hypertextbook, https://physics.info/coulomb/practice.shtml
SoftSchols.com (2021, June 27), Coulomb’s Law Formula https://www.softschools.com/formulas/physics/coulombs_law_formula/218/
Wikipedia, (2021, June 27) Coulomb’s Law https://en.wikipedia.org/wiki/Coulomb%27s_law
Rohan Naik, Quora.com (2021, June 27) What is Coulomb’s law? https://www.quora.com/What-is-Coulomb%E2%80%99s-law-2
Boston University, (2021, June 27) Field and Potential from Conducting Spheres http://physics.bu.edu/~duffy/semester2/d06_potential_spheres.html
Lumenlearning.com (2021, June 27) Electrical Potential Due to a Point Charge https://courses.lumenlearning.com/physics/chapter/19-3-electrical-potential-due-to-a-point-charge/
TechTarget (2021, June 27) https://whatis.techtarget.com/definition/coulomb
Etc. The list is long.