AP Physics C Electricity : Interpreting Electric Charge Diagrams

Study concepts, example questions & explanations for AP Physics C Electricity

varsity tutors app store varsity tutors android store

Example Questions

Example Question #1 : Interpreting Electric Charge Diagrams

A charge of unknown value is held in place far from other charges. Its electric field lines and some lines of electric equipotential (V1 and V2) are shown in the diagram.

Onecharge_negative_fieldandpotentiallines

A second point charge, known to be negative, is placed at point A in the diagram. In which direction will the second, negative charge freely move?

Possible Answers:

Toward point C

It will remain stationary

Toward point A

Toward the original charge Q

Correct answer:

Toward point C

Explanation:

The original charge Q is negative, as indicated by the direction of the electric field lines in the diagram. A negative point charge of any value placed at point A will cause both charges to feel a mutually repelling force on each other. Therefore, the second charge will be repelled by the original negative charge with a force pointing radially along a line connecting the center of Q and the point A, resulting in free movement toward C. Additionally, point B is on a line of equipotential to point A; negative point charges will move from regions of lower electric potential to higher electric potential (against the direction of the electric field lines), so point B is not a viable answer.

Learning Tools by Varsity Tutors

Incompatible Browser

Please upgrade or download one of the following browsers to use Instant Tutoring: