Electrostatics-Test-Review-KEY

Electrostatics-Test-Review-KEY - Version PREVIEW...

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Unformatted text preview: Version PREVIEW Electrostatics Test Review Tubman (3141) 1 This print-out should have 44 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. Hewitt CP9 22 E11 001 10.0 points What happens to the mass of an object when it acquires a negative net charge by the trans- fer of electrons? 1. decreases 2. Unable to determine 3. Doesnt change 4. increases correct Explanation: When an object acquires a negative charge, it gains electrons, so its mass increases. Holt SF 17Rev 03 002 10.0 points A negatively charged balloon has 3 . 2 C of charge. How many excess electrons are on this bal- loon? Correct answer: 2 10 13 electrons. Explanation: Let : q =- 3 . 2 C and =- 1 . 60 10- 19 C / electron . The charge density is = q N N = q =- 3 . 2 10- 6 C- 1 . 6 10- 19 C / electron = 2 10 13 electrons . Conceptual 24 Q01 003 10.0 points Why are metals generally good conductors of electricity? 1. Metals have strong bonding with other atoms. 2. Metals have more protons. 3. Metals have free electrons in their outer shell. correct Explanation: Conceptual 24 Q05 004 10.0 points How can a hole moving through a semiconduc- tor be like an electric charge moving through the same material? 1. If an electron moves into the hole, the hole changes places with the electron. correct 2. A hole is a location of a proton. Explanation: A hole is a location of a missing electron in a crystal. Even though it is not a real particle, it is a location of positive charge. If an electron moves into the hole, the hole changes places with the electron. In this way, the hole can move through the crytal just like a charged particle. Negatively Charged Rod 005 10.0 points If a negatively charged rod is held near an uncharged metal ball, the metal ball 1. becomes negatively charged. 2. becomes polar. correct 3. is unaffected. 4. becomes positively charged. 5. Effect cannot be determined. Explanation: When the charged rod moves toward the metal ball, an electric field is created around Version PREVIEW Electrostatics Test Review Tubman (3141) 2 the ball. Electrons inside the metal ball can move freely, and move away from the area where the negatively charged rod approaches, causing a positively charged area. Thus the metal ball is now polar. Positively Charged Conductor 006 10.0 points When a positively charged conductor touches a neutral conductor, the neutral con- ductor will 1. stay neutral. 2. gain protons. 3. gain electrons. 4. lose electrons. correct 5. lose protons. Explanation: When the two conductors touch, the elec- trons in the neutral conductor will move over to the positively charged conductor, since the latter will define a region of higher potential than the neutral conductor....
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This note was uploaded on 02/26/2012 for the course PHYSICS 302K taught by Professor Irenepolycarpou during the Spring '09 term at University of Texas.

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Electrostatics-Test-Review-KEY - Version PREVIEW...

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