Module 3

Module 3—Electrical Phenomena

 

Reflect and Connect

 

Retrieve the chart of your explanations of what happened using the Van de Graaff generator at the beginning of the lesson. Now that you have explored the three methods of transferring charge, you may need to reconsider your previous explanations.

 

Before you revise your chart, you need a little background information about the charge on the top of a Van de Graaff generator.

 

The globe of the Van de Graaff generator becomes negatively charged as excess electrons are transferred from a connection to the ground. This is done as a fast-moving belt rushes by metal combs at the top and bottom of the machine. Since the globe of the Van de Graaff generator is a conductor, the excess electrons redistribute themselves evenly over the surface of the globe. These excess electrons cannot return to the base because the rubber belt and the plastic column supporting the globe are insulators.

 

It takes work to force electrons to move from the ground connection at the base to the globe at the top. This is why input energy must be supplied by the motor of the generator to rotate the rubber belt on its two pulleys. You’ll learn more about the energy required to do work on moving charges in later lessons.

 

Module 3: Lesson 1 Assignment

 

Remember to submit the answers to A 2 and A 3 to your teacher as part of your Module 3: Lesson 1 Assignment.

 

A 2. As you saw in the opening activity for this lesson, objects were placed on the globe of the Van de Graaff generator.

 

In each case, electrons were transferred from the negatively charged globe of the Van de Graaff generator to each of these objects. The result was that individual objects became negatively charged.

 

Use what you have learned in this lesson to explain the behaviour of each of these objects after the Van de Graaff generator was turned on. Submit your revised explanations for each of the following demonstrations to your teacher:

1. animal fur
2. aluminum pie plates
3. confetti

A 3. Place your explanations from A 2 alongside the explanations you developed in A 1 at the beginning of this lesson. Contrast the two sets of explanations to identify the most significant improvements that you have made to your explanations. Remember to add the answers to this question to your course folder.

 

Try This: Explaining the Behaviour of the Soap Bubbles

 

Now that you have improved upon your explanations of the first three Van de Graaff generator demonstrations, reconsider the behaviour of the soap bubbles.

 

 

The behaviour of the soap bubbles is much more complex than that of the animal fur, the pie plates, or the confetti because the soap bubbles are subject to a sequence of interconnected events.

 

These events have been organized into the four steps listed below. In each step, describe what is happening and then explain. You can check your answers by clicking on the Description and Explanation buttons.

 

Step 1: Neutral soap bubbles are attracted to the negative globe.

 

 

For more information, click on Description and Explanation.

 

 

 

Step 2: The first soap bubble collides with the globe and becomes negatively charged.

 

 

For more information, click on Description and Explanation.

 

 

 

Step 3: The repelled tiny negative droplets collide with incoming soap bubbles.

 

 

For more information, click on Description and Explanation.

 

 

 

Step 4: Incoming bubbles are repelled and move away from the negatively charged globe.

 

 

For more information, click on Description and Explanation.

 

 

 

 

Big Picture Reflection

 

Connecting Bubbles and Lightning Strikes

 

In the previous section you worked at describing and explaining what happens to a soap bubble near the negatively charged globe of a Van de Graaff generator.

 

You might be surprised to know that the principles explained in this demonstration can also be applied to lightning.

 

Read

 

Carefully read the section called “How Lightning Gets Its Charge” on page 522 of your physics textbook. As you read this section, look for similarities between lightning and the soap bubble demonstration.

 

Discuss

 

D 1. Summarize the piece from the textbook called “How Lightning Gets Its Charge” by writing or illustrating a series of steps that will concisely describe and explain what occurs in this process. Your result should be in a format similar to the steps used to describe and explain the soap bubble in the previous activity. Remember to add the answer to this question to your course folder.

 

D 2. Post your summary to the discussion area set up by your teacher. Compare your summary to at least one other explanation produced by another student. Identify similarities and differences between your work and the work of other students. Remember to add the answer to this question to your course folder.

 

D 3. If you were to update your explanation of lightning based on what you learned in D 2, what changes would you make? Remember to add the answer to this question to your course folder.

 

Module 3: Lesson 1 Assignment

 

Remember to submit the answer to D 4 to your teacher as part of your assignment.

 

D 4. Use your answers to Discuss questions D 1, D 2, and D 3 to revise your explanation of how lightning gets its charge. Submit your revised summary to your instructor as part of your assignment.

 

 

Module 3: Lesson 1 Assignment

 

Remember to submit your Module 3: Lesson 1 Assignment, including question A 4 to your teacher for marks.

 

A 4. Do question 10 of “10.1 Check and Reflect” on page 523 of your physics textbook.

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