Lecture_03_(Chap.15)

# Lecture_03_(Chap.15) - Question 1(Chap 14 What is the...

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1 What is the direction of the electric field at location X , due to the dipole? Question 1 (Chap. 14) A C B E D - + X

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2 Question 2 (Chap. 14) Locations 1 and 2 are equidistant from the center of the dipole. At which location is the magnitude of the electric field larger ? A. at location 1 B. at location 2 C. magnitudes are the same + 1 2 d d -
Chapter 14 Matter and Electric Fields 3

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Matter is made out of atoms. Atom contains charged particles: electrons ( -e ), protons ( +e ) Neutral atom: number of electrons and protons is equal: Example : Hydrogen atom: 1 proton, 1 electron net charge = (+e) + (-e)=0 Sodium atom: 11 protons, 11 electrons Sodium atom (Na) can lose an electron: Sodium ion (Na + ): (+11e) + (-10e) = +e Ordinary matter is electrically neutral. However, can be charged by adding/removing charged particles Net Charge If remove all electrons from human body, Q=30kg/(1.7x10 -27 kg)*1.6x10 -19 C=3x10 9 C. Repelling force between you and me: F = 9x10 9 *(3x10 9 ) 2 /10 2 = 10 27 N Even if you were on the moon: F = 9x10 9 *(3x10 9 ) 2 /(4x10 8 ) 2 = 5x10 11 N Even if you were on the moon: F = 9x10 9 *(3x10 9 ) 2 /(1.5x10 ) 2 = 5x10 6 N = 2,000 tons
The net charge of a system and its surroundings cannot change If one object gets charged positively, there must be an object which gets charged negatively. Conservation of Charge The net electric charge is conserved in any physical process. Charge can be transferred from one object to another. Annihilation : e + + e = γ + γ 5

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How can we decide if a piece of invisible tape is electrically charged? Charge creates E field; detected by another charged object: • the magnitude of E is proportional to amount of charge • the magnitude of E decreases with distance • the direction of E points directly away or to the charge E q F = force has the same properties as E Observing Electric Interactions 6
How would we determine the sign of the charge?

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## This note was uploaded on 04/23/2011 for the course PHYS 272h taught by Professor Staff during the Spring '08 term at Purdue.

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Lecture_03_(Chap.15) - Question 1(Chap 14 What is the...

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