Questions About Electric Forces Practice Test

Two plastic rods are rubbed with cloth and then brought near each other. Sometimes they repel and sometimes they attract depending on how they were charged. A student wants to investigate how distance affects electric force strength using only the rods and a ruler. Which question is most investigable?

A student writes this investigation question after seeing a rubbed balloon attract paper: “How does rubbing time and distance and wall material affect electric force?” Which change would make the question more testable and focused?