1. Module 3

1.10. Lesson 2

Module 3 Lesson 2

Module 3—Electrical Phenomena

 

Lesson 2—Investigating Coulomb’s Law

 

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The illustration shows a head and shoulders picture of a young woman standing at a lookout in Sequoia National Park, the mountain scenery visible in the background. Her hair is standing on end.

© NOAA US Gov

This is the young woman at the observation platform of a national park whom you met in the previous lesson. Recall that charges in a nearby thundercloud caused her hair to stand on end. Although the exact details of what happened that day are unknown, the following diagram shows what this scene may have looked like from a different perspective.

 

An illustration shows a negatively charged cloud above people on a tall hill. A hiker in the valley below is about four times as far from the negative charges in the cloud as the people on the hill. The negatively charged cloud causes a charge separation on the people on the hill and the hiker below. The charges in the environment are represented by negative and positive signs in the cloud, negative signs in the ground, and positive signs just above the ground and surrounding the people.

This illustration shows a hiker standing far below the platform, somewhere in the valley. Since the hiker is about four times as far from the negative charges in the cloud, the hiker is in a much safer location than the people on the platform. For the hiker in the valley, it would be unlikely that the charge in the cloud could induce a charge on strands of hair. There wouldn’t be a large enough force to make these hairs stand on end. If the distance were four times farther, how would the electrostatic force be affected? Would the force be ¼ as large for the hiker as for the people on the observation platform?

 

Charles de Coulomb, in 1785, investigated the precise relationship between electrostatic forces and distance of separation. Coulomb was a former military engineer. He used his engineering skills to design and build a precision device to explore the variables that affect electric forces. The results of his work provide a precise description of the electric force that exists between two charged objects separated by a known distance.

 

In this lesson you will focus on the following essential questions:

  • What is Coulomb’s law, and how was this law determined using the results of experiments?
  • Can Coulomb’s law predict the effect on electrostatic force if the distance of separation increases by a known amount? What does the answer to this question suggest about lightning safety?
Module 3 Lesson 2 AssignmentModule 3: Lesson 2 Assignment

 

Your teacher-marked Module 3: Lesson 2 Assignment requires you to submit a response to the following questions:

  • Assignment—A 1 and A 2

You must decide what to do with the questions that are not marked by the teacher.

 

Remember that these questions provide you with the practice and feedback that you need to successfully complete this course. You should respond to all the questions and place those answers in your course folder.