# chap20 - 1 PHYS 1302 Introductory Physics II Chapter...

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Unformatted text preview: 1 PHYS 1302 Introductory Physics II Chapter 20:Electric potential & electric potential energy 7/9/09 LAU/PHYS 1302 Lecture 2 12-2 Topics s Electric energy and potential (quantitative) s Electric potential of a point charge (quantitative) s Electric potential and energy of a parallel plate capacitor (quantitative) s Equipotential surface s Complementarity of electric force and potential s Atmospheric electricity (Lightning and grounding) 7/9/09 LAU/PHYS 1302 Lecture 2 12-3 There is energy in electricity! 7/9/09 LAU/PHYS 1302 Lecture 2 12-4 A well-known example of potential Energy 7/9/09 LAU/PHYS 1302 Lecture 2 12-5 Electric potential energy s Energy is a useful concept in physics because r Energy is a scalar r Energy is conserved s Electric energy is another form of energy s Potential energy can be defined for electric forces r Potential energy change is a function of only start and end positions, independent of the path taken r Only potential energy difference is meaningful s Energy is a physical concept complementary to force 7/9/09 LAU/PHYS 1302 Lecture 2 12-6 Electric energy between two point charges qq U k r = The electric (electrostatic ) energy between the two point charges is The electrostatic energy is a scalar, measured in Joules (J). The energy is in the form of potential energy (recoverable), like that in a compressed or stretched spring. 7/9/09 LAU/PHYS 1302 Lecture 2 12-7 Electric potential: standardizing electric energy q k q U q r V k q q r = = = The electric potential is electric energy per unit charge, measured in Joules per coulomb (J/C), also known as 1 volt (V). The electric potential is a field, created by the point charge q. The electric potential energy of any charge q 0 due to q is q V U q V = 7/9/09 LAU/PHYS 1302 Lecture 2 12-8 Exercise 20-2 What is the potential due to a point charge of 6.80 × 10-7 C at a distance of 2.60 m? V = kq r = (8.99 × 10 9 N ⋅ m 2 / C 2 )(6.80 × 10- 7 C ) 2.60 m = 2350 V 1 J/C = 1 V 7/9/09 LAU/PHYS 1302 Lecture 2 12-9 Electric potential of point charges V = kq r ( a ) q > ( b ) q < 7/9/09 LAU/PHYS 1302 Lecture 2 12-10 Superposition of potentials: example 20-3 ( 2 ) ( ) (1.0 m ) kq k q V x x x- = +- 7/9/09 LAU/PHYS 1302 Lecture 2 12-11 Superposition of potentials: example 20-3 V ( x ) = kq 1.0 m + x + kq (1.0 m- x ) 7/9/09 LAU/PHYS 1302 Lecture 2 12-12 What is 1 electron-volt?...
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## This note was uploaded on 04/10/2010 for the course PHYS 1102 taught by Professor Lau during the Spring '10 term at Houston Baptist.

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chap20 - 1 PHYS 1302 Introductory Physics II Chapter...

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