Static Electric Charge and Conductors

Static Electric Charge and Conductors

By Rachel Wampler

• Nucleus

  • Protons - positive charge

  • Neutrons - no charge, but same mass as proton

• ​​Electron Cloud

  • Electron - negative charge, little mass

  • q_e = -1.60 x 10^-19 C

    • Unit of charge: Coulomb (C)

    • smallest charge discovered

    • Electricity is quantized --> comes in discreet numbers

    • the fundamental unit of charge

• In nature atoms have no net charge

  • # protons = # electrons​

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An Atom:

Multiple Choice

How many electrons does it take to make a charge of -4x 10^-6 C?

• 1.6 x 10^-19

• 2.5x 10^-13

• 3.2 x 10^-13

• 4.0 x 10^-6

Multiple Choice

What is the mass of 2.5x 10^-13 electrons if m_e = 9.11 x 10^-31 kg?

• 2.5 x 10^-13

• 1.6 x 10^-19

• 2.28 x 10^-17

• 9.11 x 10^-31

• During any process, the net electrical charge of a closed system remains constant

• Like charges repel

• Unlike charges attract

  • The attraction and repulsion are forces and can be used with Newton's Laws and other dynamics problems​

Law of Conservation of Charge

• Most heat conductors are also electrical conductors

• METALS​

• Conductors let electrons flow easily

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Conductors and Insulators

• Electricity can flow through objects

• Plastic

• Wood

• Rubber​

• Insulators are very poor conductors

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Open Ended

Why do metals make good conductors?

• Negative charged rod gives some electrons to sphere

• Sphere becomes negatively charged until charges are equal​

Charging by Contact

• Charge without touching

• Charged rod comes near neutral sphere

• The like charges are repelled to the other side of the sphere

• A grounding wire lets the charges escape from the sphere

• The grounding wire is removed, then the charged rod

• Sphere is charged​

Charging by Induction

Insulators vs. Conductors

What if the spheres were plastic instead of metal?

• Electrons wouldn't flow

• The surface would become slightly charged as the electrons in each individual atom rearrange, but no overall effect

• Static cling is made by this effect​