Chapter 21 - charges are closer to the negatively charged...

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Electric charge: Chapter 21 Protons have positive charge Electrons have negative charge Opposite signs attract Similar signs repel Electric field – used to calculate force
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Example: LITHIUM (Li) Atom : electrically neutral 3 protons and 3 electrons. Positive ion : missing one electron so net charge is positive Negative ion : has added electron so net charge is negative
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Two positive charges or two negative charges repel each other. A positive charge and a negative charge attract each other.
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Copper is a good conductor of electricity; Glass and nylon are good insulators Metal ball is charged negatively as shown in A B A C
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Charging a metal sphere by induction: Charges are free to move in a conductor but are tightly bound in an insulator. The earth (ground) is a large conductor having many free charges .
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In an insulator the charges can move slightly (called polarization of the insulator). A piece of paper is attracted to a charged comb because the positive
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Unformatted text preview: charges are closer to the negatively charged comb (in the upper figure). CHARGED COMB ATTRACTS PAPER A practical example FORCE between two charges is given by Coulomb’s Law : Coulomb’s Law Coulomb’s Law: | F | = k | Q q o | / r 2 Rearranged: | F | = | q o [k Q/r 2 ] | Gives us: F = q o E where the electric field E is: | E | = | k Q / r 2 | Electric field E ELECTRIC FIELD LINES START AND END AT ELECTRIC CHARGES An electric charge is surrounded by an electric field just as a mass is surrounded by a gravitational field. Forces on electron beam in a TV tube (CRT) F = Q E and F = m g (vector equations) Application: TV tube with electron-deflecting charged plates (orange) F = Q E An ELECTRIC DIPOLE consists of a +q and –q separated by a distance d. ELECTRIC DIPOLE MOMENT is p = q d ELECTRIC DIPOLE in E experiences a torque: τ = p d E ELECTRIC DIPOLE in E has potential energy: U = - p d E ELECTRIC DIPOLE...
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This note was uploaded on 05/30/2011 for the course PHYS 150 taught by Professor Anz-meador during the Spring '08 term at Embry-Riddle FL/AZ.

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Chapter 21 - charges are closer to the negatively charged...

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