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Potential Difference

Potential Difference. Potential. A charged particle has potential energy due to its position relative to another charged object (Electric Potential Energy) The + particle has potential energy at position A

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Potential Difference

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  1. Potential Difference

  2. Potential • A charged particle has potential energy due to its position relative to another charged object (Electric Potential Energy) • The + particle has potential energy at position A • Once the particle moves to B all PE is changed to KE • (-) plate has low potential, (+) plate has high potential

  3. Definition • Potential (V) is defined as the PE per charge V = PE/ q • Units J/C 1 J/C = 1 Volt (V) • Note that only changes in PE are measurable – called Potential Difference • Potential difference = Voltage

  4. Equation • ΔPE = qV • Voltage is a measure of how much energy an electric charge can acquire • Since change in energy is the ability to do work, it is also a measure of how much work • W = qV

  5. Measurement • Voltmeter – instrument used to measure V between 2 points

  6. C:\My Documents\voltage.asx

  7. Example 1 • An electron in the picture tube of a TV is accelerated from rest through a potential difference of +5000V a) what is the change in PE b) what is the electron’s speed c) how much work is done?

  8. Example 2 • The terminals of a 12V battery differ in potential by 12V. Suppose that a wire is connected between the + and – terminal and 3.0 C of charge travels between them. How much work is done?

  9. Example 3 • An electron loses 3.45 x 10-16J of PE as it moves from plate A to B in a computer monitor. What is the voltage between the plates and which plate has the highest potential?

  10. Electric Field • Amount of potential difference (voltage) is related to the strength of the electric field • W = qV • W = Fd • F = qE • qV = qEd • V = Ed or E = V/d

  11. Units of Electric Field • Either N/C or V/m

  12. Example • Two parallel plates are charged to 50V. If the plates are separated by .050m, what is the electric field they produce?

  13. Small Energy Unit • J is traditional unit of energy, but with very small particles this unit appears very large • Smaller unit of energy is used for these called the electron volt (eV) • Before doing a problem, always change eV to J 1 eV = 1.6 x 10-19 J

  14. Example • What potential difference is needed to give a particle of charge of 3μC a total of 3.54 x 109 eV of energy?

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