A laboratory whiteboard displays an electric-field line diagram described as follows
PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Electric Force Field and Potential · Electric Force Field and Potential
Problem
A laboratory whiteboard displays an electric-field line diagram described as follows.
• Twelve evenly spaced lines emanate radially outward from a small metal sphere labeled A.
• Six lines terminate uniformly on a nearby small plastic sphere labeled B.
• No other lines originate from or terminate on any other object.
• At a location P midway between the centers of the two spheres, the field lines point directly from A toward B, and the line density there appears to be greater than at a location Q that is twice as far from A along the same straight line.
Answer the following, justifying each response with explicit reference to properties of electric-field lines.
(a) Determine the algebraic sign of the charge on sphere A and on sphere B.
(b) Calculate the ratio ∣qA∣:∣qB∣ of the magnitudes of the charges on the two spheres.
(c) Describe the direction of the electric force that would act on a small positive test charge placed at P, and explain how the diagram supports your answer.
(d) Explain qualitatively why the electric-field magnitude at P is greater than at Q, even though both points lie on the same straight line extending from sphere A.