Ch17-h3-solutions - pan (zp695) Ch17-h3 chiu (56565) 1 This...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: pan (zp695) Ch17-h3 chiu (56565) 1 This print-out should have 27 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 2) 10.0 points The potential di ff erence from one end of a 1 cm-long wire to the other in a circuit is V = V B- V A = 2 . 1 V , as shown in the figure below. A B 1 cm Which end of the wire is at the higher po- tential? 1. The ends are at the same potential. 2. A 3. B correct Explanation: Since V B- V A is a positive number, it is clear that B is at the higher potential. 002 (part 2 of 2) 10.0 points What is the magnitude and direction of the field E inside the wire? (Since this is a 1D problem, the sign of your answer will indicate the direction.) Correct answer:- 210 V / m. Explanation: It should be clear that E points toward the left, since E points toward the lower potential. For a constant electric field, V =- E d =- E . For a path from A to B, = x, , . V =- E x x E x =- V x =- 2 . 1 V . 01 m =- 210 V / m . 003 10.0 points In a television picture tube, electrons are boiled out of a very hot metal filament placed near a negative metal plate. These electrons start out nearly at rest and are accelerated toward a positive metal plate. They pass through a hole in the positive plate on their way toward the picture screen, as shown in the diagram. Hot filament-------- + + + + + + + + + + Plate Plate F = eE E v = ? L The high-voltage supply in the television set maintains a potential di ff erence of 14500 V between the two plates, what speed do the electrons reach? Use m e = 9 . 11 10- 31 kg and q e = 1 . 6 10- 19 C and assume that this is not relativistic. Correct answer: 7 . 13674 10 7 m / s. Explanation: The net energy remains constant through- out the whole process. We can use the follow- ing train of logic: pan (zp695) Ch17-h3 chiu (56565) 2 E = 0 U + K = 0 q V + K = 0 (- e ) V + K = 0 K = e V = (1 . 6 10- 19 C)(14500 V) = 2 . 32 10- 15 J . Then K = K f- K i = 1 2 mv 2 f- v f = 2 K m = 2(2 . 32 10- 15 J) 9 . 11 10- 31 kg = 7 . 13674 10 7 m / s . 004 (part 1 of 2) 10.0 points What is the maximum possible potential (rel- ative to infinity) of a metal sphere of 19 cm in air? Remember that the breakdown electric field strength for air is roughly 3 10 6 N / C and also take 1 4 = k = 9 10 9 N m 2 / C 2 . Correct answer: 5 . 7 10 5 V. Explanation: The problem indicates that E max at the sur- face of the sphere is 3 10 6 N / C. Now, using the equations for electric field and potential for a spherically distributed charge, we have E = 1 4 Q R 2 Q = (3 10 6 N / C)(19 cm) 2 9 10 9 N m 2 / C 2 = 1 . 20333 10- 5 C ....
View Full Document

This note was uploaded on 02/21/2012 for the course PHY 303K taught by Professor Turner during the Spring '08 term at University of Texas at Austin.

Page1 / 11

Ch17-h3-solutions - pan (zp695) Ch17-h3 chiu (56565) 1 This...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online