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Unformatted text preview: CH 15 HW 3 F2008 10/30/08 11:09 PM WebAssign CH 15 HW 3 F2008 (Homework) Current Score: 13 out of 13 Due: Wednesday, September 17, 2008 12:30 PM EDT Description Reading: Sec. 15.6-15.9. Electric field of charge distributions Read the assigned pages before trying the questions. BAKER KRISTINE NICOLE PY 208M, section 004, Fall 2008 Instructor: Laura I. Clarke The due date for this assignment is past. Your work can be viewed below, but no changes can be made. Extensions are no longer available for this assignment. (Automatic Extensions are only available within 2 days of the assignment due date.) View Key 1. 2/2 points A hollow ball of radius 7 cm, made of very thin glass, is rubbed all over with a silk cloth and acquires a negative charge of -9.5e-08 C which is uniformly distributed all over its surface. Location A, shown in the diagram, is inside the sphere, 1 cm from the surface. Location B, shown in the diagram, is outside the sphere, 2 cm from the surface. There are no other charged objects nearby. Which of the following statements about Eball , the magnitude of the electric field due to the ball, are correct? Select all that apply. All of the charges on the surface of the sphere contribute to Eball at location A. A hydrogen atom at location A would polarize because it is close to the negative charges on the surface of the sphere. At location B Eball is 2.14 106 N/C.
http:[email protected][email protected] Page 1 of 4 CH 15 HW 3 F2008 10/30/08 11:09 PM At location B Eball is 2.14 106 N/C. At location A Eball is 0 N/C. 2. 6.5/6.5 points A small, thin, hollow spherical glass shell of radius R carries a uniformly distributed positive charge +Q, as shown in the diagram above. Below it is a horizontal permanent dipole with charges +q and -q separated by a distance s (s is shown greatly enlarged for clarity). The dipole is fixed in position and is not free to rotate. The distance from the center of the glass shell to the center of the dipole is L. The charge on the thin glass shell is +8e-09 coulombs, the dipole consists of charges of 2e-11 and -2e-11 coulombs, the radius of the glass shell is 0.15 m, the distance L is 0.45 m, and the dipole separation is 2e-05 m. Calculate the net electric field at the center of the glass shell. The x axis runs to the right, the y axis runs toward the top of the page, and the z axis runs out of the page, toward you. = < 3.95e-5 , 0 , 0 > N/C http:[email protected][email protected] Page 2 of 4 CH 15 HW 3 F2008 10/30/08 11:09 PM If the upper sphere were a solid metal ball with a charge +8e-09 coulombs, what would be the net electric field at its center? = < 0 , 0 , 0 > N/C Which of the diagrams below best shows the charge distribution in and/or on the metal sphere? E A B C D E F G H J K 3. 4.5/4.5 points http:[email protected][email protected] Page 3 of 4 CH 15 HW 3 F2008 10/30/08 11:09 PM In a cathode-ray tube (CRT), an electron travels in a vacuum and enters a region between two "deflection" plates which have equal and opposite charges. The dimensions of each plate are 13 cm by 3 cm, and the gap between them is 2.5 mm (not to scale in the diagram). During a 0.001 s interval while it is between the plates, the change of the momentum of the electron is < 0,4.80e-17,0 > kg m/s. What is the electric field between the plates? Hint: remember the Momentum Principle (the relationship between Impulse and change in momentum.) =< 0 , -299625.47 , 0 > N/C What is the charge (both magnitude and sign) of the upper plate? q = 1.03e-8 C http:[email protected][email protected] Page 4 of 4 ...
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This note was uploaded on 10/30/2008 for the course PY 208M taught by Professor Chabay during the Spring '08 term at N.C. State.
- Spring '08