
Study with the several resources on Docsity
Earn points by helping other students or get them with a premium plan
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Community
Ask the community for help and clear up your study doubts
Discover the best universities in your country according to Docsity users
Free resources
Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors
The directions and problems for a university physics exam held at the university of california, berkeley during the spring 2004 semester for physics 110b (strovink). The exam covers topics such as relativistic mechanics, electric fields, and potentials. Students are required to solve three problems, which have unequal weight, using only specified materials and without calculators or laptops. The problems involve finding the rapidity and motion of a charged particle in a uniform electric field, the scalar potential seen by an observer due to a moving charged particle, and the leading term in the multipole expansion of the electrostatic potential due to a line charge distribution.
Typology: Exams
1 / 1
This page cannot be seen from the preview
Don't miss anything!
University of California, Berkeley Physics 110B Spring 2004 (Strovink)
EXAMINATION 2
Directions: Do all three problems, which have unequal weight. This is a closed-book closed-note examexcept for Griffiths, Pedrotti, a copy of anything posted on the course web site, and anything in your own original handwriting (not Xeroxed). Calculators are not needed, but you may use one if you wish. Laptops and palmtops should be turned off. Use a bluebook. Do not use scratch paper ā otherwise you risk losing part credit. Show all your work. Cross out rather than erase any work that you wish the grader to ignore. Justify what you do. Express your answer in terms of the quantities specified in the problem. Box or circle your answer.
Problem 1. (35 points) A positive point charge q of rest mass m is sub- jected to a uniformconstant electric field E 0 pointing in the Ėx direction (as observed in the laboratory). This force causes its (relativistic) momentum to increase linearly with laboratory time t.
(a.) (15 points) At t = 0 the charge is at rest at the origin. Thereafter, show that sinh Ī· = Ļ 0 t, where Ī· is the chargeās rapidity and Ļ 0 is a constant. De- termine Ļ 0.
(b.) (20 points) For t > 0 show that the charge moves according to Ļ 0 c
x(t) =
1 + Ļ^20 t^2 ā 1.
Problem 2. (35 points) At t = 0 at the origin of a laboratory coordinate system, a point particle of charge q has velocity βc directed along the Ėz axis. It has been moving with that constant velocity for a long time.
(a.) (20 points) At t = 0, starting with the Coulomb potential in the particleās rest frame, and using the rules for relativistic transforma- tion both of coordinates and of em potentials (in Lorentz gauge), find the scalar potential V seen by an observer located at Cartesian coordinates (x, 0 , z), where V (ā) ā” 0. Express V in terms of β, x, z, and constants.
(b.) (15 points) As seen at t = 0 by the labora- tory observer, is āāV expected to point in the radial direction? Explain.
Problem 3. (30 points) A thin insulating rod, running from z = āa to z = +a, carries a static line charge density (Coul/m)
Ī»(z) = Ī» 0 cos
Ļz a
Find the leading term only in the multipole expansion of the electrostatic potential V (r). Express your answer in terms of the observerās polar angle Īø and the observerās distance r to the origin.