Potential Difference

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# Potential Difference - PowerPoint PPT Presentation

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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Presentation Transcript

### 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
• Once the particle moves to B all PE is changed to KE
• (-) plate has low potential, (+) plate has high potential
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
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
Measurement
• Voltmeter – instrument used to measure V between 2 points
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?
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?
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?
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
Units of Electric Field
• Either N/C or V/m
Example
• Two parallel plates are charged to 50V. If the plates are separated by .050m, what is the electric field they produce?
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

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