Order the steps: net force on one charge among many
Exercise and reference answers
- Steps
- Take the charge of interest and one other charge
- Apply Coulomb's law to that pair alone
- Fix the direction along the line joining them
- Repeat for every other charge in the assembly
- Add all those forces as vectors to get the net force
Explanation
Superposition is a procedure, and doing it in this order avoids sign errors. Source: syllabus Physics Part I, Ch 1 Electric Charges and Fields.