Static Electricity

Basic Electricity

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  • Question 1

    What does it mean for an object to have an electric charge? Give an example of an object receiving an electric charge, and describe how that charged object might behave.

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  • Question 2

    How many electrons are contained in one coulomb of charge?

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  • Question 3

    What is happening when two objects are rubbed together and static electricity results?

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  • Question 4

    How many electrons are there in 2 ×10−5 coulombs of charge? Determine the answer without using a calculator, and express the answer in scientific notation!

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  • Question 5

    If a positive charge is forcibly moved closer to another positive charge, mechanical work must be performed. This is analogous to compressing a spring: work must be done to cause motion against the natural repulsion of the system:

    This mechanical work becomes “stored” in the electric field between the charges, and is a form of potential energy. This, again, is similar to a mechanical spring, where the work done in compressing a spring is “stored” as potential energy in its compressed state.

    Define voltage in terms of the change in potential energy resulting from this forceful motion of the charge, the way a physicist would.

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  • Question 6

    A co-worker of mine was once installing sheet-styrofoam insulation in the walls of his new garage. The sheets of insulation came wrapped together in bundles for easy transport and storage.

    One side of each sheet was covered in aluminum foil. This acted as a reflective surface for infra-red (heat) radiation, and improved the effectiveness of the insulating panel. It also happened to function as a conductor of electricity, much to the dismay of my friend.

    My friend found that the sheets were physically stuck together by the force of static electric charges when they were delivered to his house. Upon trying to pry two of them apart from each other, he received a surprisingly large electric shock from touching the aluminum foil surfaces of the respective panels! Explain how the physical work he did in separating the panels from each other became manifest as voltage, based on your knowledge of voltage, work, and electric charges.

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  • Question 7

    Lightning is a spectacular example of naturally-generated static electricity. Explain how the vast static electric charges that cause lightning are formed by natural processes, and how those processes relate to the function of a device called a Van de Graaff generator.

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  • Question 8

    A special kind of electric light known as a neon bulb is an excellent tool for demonstrating the presence of static electricity, and is easily obtained at most electronics supply shops:

    When a large enough static electric charge is applied between the two wires of the neon bulb, the neon gas inside will “ionize” and produce a colored flash of light. Experiment with generating your own static electricity and then making the bulb flash. Hint: it may be easier to see the bulb’s flash if the room is dark.

    What conditions produce the brightest flash from the bulb? What materials and techniques work best for producing strong static electric charges?

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  • Question 9

    If a neon bulb is used as a visual indicator of static electricity, it will be noticed that only one of the two metal electrodes inside the glass envelope glows upon discharge. Why is this? Why don’t both electrodes glow?

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  • marnen February 25, 2020

    Someone clearly did an ill-advised search and replace turning “element” to “entry”, so this page mentions “entryary charge” instead of “elementary charge” and “the entry carbon” instead of “the element carbon”. Please fix this.

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  • ACour83 May 28, 2020

    What is the math behind Q4? Showing the work might be a good idea.

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    • RK37 May 28, 2020
      There are 6.25 × 10^18 electrons per coulomb. In Q4, we are given coulombs (2 × 10^-5) and must calculate electrons. Thus, we need to multiply the two numbers, so that the coulomb unit cancels out and we are left with electrons: 6.25 × 2 = 12.5, and if we add the two exponents we get 13, so the number of electrons is 12.5 × 10^13. Then we move the decimal one place to obtain 1.25 × 10^14.
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