# Electric Field Due to a Line of Charge

Recommended for High School through College.

## 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.

## Software for Experiment

This experiment uses Logger *Pro* software for video analysis. The video for analysis is included with the lab book.