Electric Field Due to a Line of Charge

Introduction

Consider a thin insulated rod that carries a known negative charge Q_rod that is uniformly distributed. It is possible to determine the electric field along a line perpendicular to the rod that passes through its center using the following equation – often derived in introductory texts:

where L is the length of the charged part of the rod, r is the distance from the test charge to the center of the charged part of the rod, and Q_rod is its total charge. The constant k is the well-known Coulomb constant.

Objectives

In this activity, you will

• Examine a digital movie of a charged rod exerting a force on a hanging “test charge” along with a Logger Pro analysis to determine if the theoretical equation describes the relationship between r, L and the measured electric field, at the location of the test charge.