Coulomb's law remains tricky to test at home

A physics enthusiast recounts a personal drive to gain "fluency" with physical laws by testing them with simple, real-world experiments. Motivated by textbook advice to think about how laws are measured, the writer probes Coulomb’s law by reasoning from first principles: the force must depend on the two charges and their separation, vanish if one charge is zero, and be symmetric between bodies. That reasoning narrows the form to a product of charges times some function of distance, and the author questions why the charge dependence is linear and why the distance dependence is an inverse square, noting historical doubts and analogies with gravity and light intensity.

Practical attempts to test the law at home expose the difficulties. The writer describes efforts to charge conductors, split charge by contact, and build a makeshift electroscope from a jar, insulated wire, and aluminum foil, observing foil leaves repel when charged. Key problems are non‑quantitative charging, humidity and charge decay, and the challenge of creating equal, repeatable charges without a torsion balance. A commenter is cited to justify the linear charge dependence experimentally (doubling one charge doubles the force), leaving the author still seeking a robust, simple setup that could convincingly verify the inverse‑square behavior.