Lines of charge: Two long straight parallel lines, #1 and #2, carry uniform positive linear charge densities. The charge density on line #2 is twice as great as the charge density on line #1. The locus of points where the electric field due to these lines is zero is
A) along a line between the lines closer to line #2 than line #1.
B) at a point midway between the lines.
C) along a line perpendicular to lines #1 and #2.
D) along a line between the lines closer to line #1 than line #2.

Question

Quizplus · Accepted Answer

The electric field is zero at a point where the electric fields due to the two lines cancel each other out. Since line #2 has a greater charge density, the point where this cancellation occurs must be closer to line #1, as the electric field strength is inversely proportional to the distance from the charge.

Lines of Charge: Two Long Straight Parallel Lines, #1 and #2