A student maps the electric field around a single isolated positive point charge by…
PHYSICS · Single correct · AP · Physics 2: Algebra-based · Electric Force Field and Potential · Electric Force Field and Potential
Problem
A student maps the electric field around a single isolated positive point charge by measuring the field at equally spaced grid points. The arrows are longest near the charge and become progressively shorter at greater distances, while the spacing between adjacent arrows remains constant. Which of the following best explains why the electric field is strongest near the charge?
(a) The mapping grid is denser near the charge, so overlapping arrows appear longer even though the field is uniform.
(b) The electric-field magnitude obeys Coulomb’s law, being inversely proportional to the square of the distance from the charge, so points closer to the charge have larger field vectors.
(c) According to Coulomb’s law, the electric-field strength is inversely proportional to the distance (not the distance squared) from the charge, so halving the distance approximately doubles the field magnitude.
(d) A larger test charge must be placed near the source to obtain a measurable reading, producing stronger forces and therefore longer arrows there.