Vernier Software and Technology
Vernier Software & Technology

Electric Field Due to a Line of Charge


Consider a thin insulated rod that carries a known negative charge Qrod 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:

\vec E_{{\text{rod}}}^{{\text{theory}}} = \frac{{\left( {k{Q_{{\text{rod}}}}} \right)}}  {{r\sqrt {{r^2} + {{(L/2)}^2}} }}\hat i

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 Qrod is its total charge. The constant k is the well-known Coulomb constant.


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, \vec E_{{\text{rod}}}^{{\text{meas}}} 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.

Physics with Video Analysis

See other experiments from the lab book.

1Rolling Ball
2Big and Small: How to Scale an Image
3Velocity Change
4Velocity and Speed
5Velocity and Acceleration
6Three Movies: Determining Constant Acceleration
7Demon Drop: A Mathematical Modeling Activity
8Jumping on the Moon
92D Vectors: Pool Ball Displacement, Velocity, and Speed
10Galileo's Projectile I: Using 17th Century Techniques
11Galileo's Projectile II: Using Contemporary Techniques
12Projectile Motion Vectors
13Frictional Slowing
14Impulsive Juggling
15Center of Mass Motions
16Finding a Spring Constant
17Net Work - Kinetic Energy Theorem
19Slinky Wave Speeds
20Superposition of Slinky Waves
21A Wave Pulse Equation
22Doppler Effect: Surface Water Waves
23Doppler Effect: Sound Waves
24A Heat Engine: Relating Work to the P-V Cycle
25Coulomb's Law for Two Charged Spheres
26Discharge Rate
27Electric Field Due to a Line of Charge
28Resistance and Ohm's Law
29Parallel Plate Capacitor: Potential Difference vs. Spacing
30Wiring Capacitors in Series and Parallel
31Using RC Decay to Determine Capacitance
32Exploring Faraday's Law
33Snell's Law of Refraction

Experiment 27 from Physics with Video Analysis Lab Book

<em>Physics with Video Analysis</em> book cover

Included in the Lab Book

Vernier lab books include word-processing files of the student instructions, essential teacher information, suggested answers, sample data and graphs, and more.

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