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Loo Ow (think Hawaii)

Loo Ow (think Hawaii). Two metal spheres, A and B, possess charges of 1.0 microcoulomb and 2.0 microcoulombs , respectively. In the diagram below, arrow F represents the electrostatic force exerted on sphere B by sphere A.

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Loo Ow (think Hawaii)

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  1. Loo Ow(think Hawaii) • Two metal spheres, A and B, possess charges of 1.0 microcoulomb and 2.0 microcoulombs, respectively. In the diagram below, arrow F represents the electrostatic force exerted on sphere B by sphere A. • Draw the magnitude and direction of the electrostatic force exerted on sphere A by sphere B

  2. Please Turn in Do Nows

  3. Objectives • What is Voltage?

  4. Homework- Finish Worksheet • (yes on the weekend – we are a week behind – I was thinking of giving the test on the weekend!)

  5. End of 4.1.4 - PRACTICE

  6. Storing Electrical Energy 4.1.5 Electrical Potential (Voltage)

  7. - - Electrical PE To increase PE + + + To decrease PE + + +

  8. Calculating Potential Difference • Amount of potential difference: • WORK DONE PER UNIT CHARGE • 1 VOLT = 1 J/C

  9. Example #1 • 6.0 joules of work are done in pushing an object with +3.0 coulombs of charge toward a charged plate. • What type of charge does the plate have on it? • How much potential energy was stored in the electric fields? • How much electrical potential was generated? V = W/q V = 6.0 J / 3.0 C V = 2.0 V Positive 6.0 J

  10. Example #2 • An object with a 2.0 coulomb charge is accelerated through a potential difference of 10 volts. • How much kinetic energy does the object gain? V = W/q W = Vq W = (10 V)(2.0 C) = 20 J

  11. What is Voltage? • In electrical fields, we will want to think in terms of the potential energy per unit of charge. Near the earth's surface the potential energy of a mass, m, h meters above the surface is mgh. • The potential energy per unit mass is just gh. • Voltage is the potential energy per unit charge for a charge in an electrical force field.

  12. Those wacky scientists… • Some scientists work with electrons and protons all day long. Rather than using numbers like 4.8 x 10-19 all day, they have an easier way to think about things. • It might not always be easier for us.

  13. Electron-volts • Alternate unit for work/energy: • Raises 1e to an electrical potential of 1 V • 1 eV = 1.6 x 10-19 J What is the energy needed to raise two electrons to a potential of 1.0 volt? What is the energy needed to raise four electrons to a potential of 2.5 volts? V = W /q 1.0 V = W / 2e W = 2.0eV V = W /q 2.5 V = W / 4e W = 10 eV

  14. Example #3 • An electron travels a distance of 2.0 x 10-3 meter as its electrical potential is raised by 300 volts. • How much work is done on the electron? V = W/q 300 V = W / 1.6 x 10-19 C W = 4.8 x 10-17 J V = W/q 300 V = W / 1e W = 300 eV

  15. End of 4.1.5 - PRACTICE

  16. Lab # Electrostatic Cycle

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