FORM A
PHYS 272H Spring 2011 EXAM-I There are two parts to the Exam: Problems 1-7 are multiple-choice problems (70 points), and Problem 8 is a comprehensive problem to be hand-graded (30 points). The Answer-Sheet is the last page (both multiple-choice and
Chapter 22
Patterns of Fields in Space of Fields in Space
Electric flux Gausss law Amperes law Maxwell equations
1
Patterns of Fields in Space
Wh What is in the box?
no charges?
vertical charged plate?
2
Patterns of Fields in Space
Box versus open surfac
Announcements
Exam 2 on 3/30 (Wednesday), 8-9:30 PM, PHYS 112. Covers materials from Chap.1821. Emphasis on concepts. Practice exam is posted on the course home page. Crib sheet provided. As same as that in the practice exam. sheet provided As same as th
Exam 2
Wednesday, March 30, 8-9:30, PHYS 112. Chap. 18-21 Emphasis on conceptual problems. on conceptual problems Practice exam on course home page.
1
Chapter 21
Magnetic Force
2
Magnetic Field of a Moving Charge
The Biot-Savart law for a moving charge 0
Exam 2
Wednesday, March 30, 8-9:30, PHYS 112. Chap. 18-21 Emphasis on conceptual problems. on conceptual problems Practice exam on course home page.
1
Ammeters, Voltmeters and Ohmmeters
Ammeter: measures current I Voltmeter: measures voltage difference V
Parallel Capacitors
Initial moment: brighter? moment: brighter? Capacitor charging Will it glow longer? it
Q/ A s Fringe field: E1 2 0 R
Capacitors in parallel effectively increase A. Initially brighter, and it will grow longer.
1
An Isolated Light Bulb
W
Twice the Length
Nichrome wire (resistive) Quantitative measurement of current with a compass
V i nAuE nAu L i2 L 1 iL 2
Current is halved when increasing the length of the wire by a factor of 2.
1
Two Identical Light Bulbs in Series
Identical light bulbs
Field due to the Battery
E
Ebends In the steady state there must be some other charges somewhere that contribute to the net electric field in such a fi way that the electric field points upstream everywhere. 1
Field due to the Battery
i nAuE
Surface charg
Chapter 19
A Microscopic View of Electric Circuits El Ci
1
Current in a Circuit
A microscopic view of electric circuits: Are charges used up in a circuit? How is it possible to create and maintain a nonzero electric it field inside a wire? What is the rol
Exam result Exam 2 result
Multiple choice Mean Standard deviation 54.0 13.5 Hand graded 18.5 7.0
1
Gausss Law: Properties of Metal
Can we have excess charge inside a metal? Proof by contradiction:
E nA
surface
q
inside
0
=0
q
inside
0
0
2
Gausss Law: Ho
Maxwells Equations (incomplete)
E ndA
q
inside
B ndA 0 E dl 0 B dl 0 I inside _ path
0
Gausss law for electricity Gausss law for magnetism Incomplete version of Faradays law Amperes law law (Incomplete Ampere-Maxwell law)
First two: integrals over a su
FORM A
PHYS 272 Spring 2010 EXAM-II There are two parts to the Exam: nine multiple-choice problems (72 points) and one comprehensive problem to be hand-graded (28 points). All pages are double-sided. The Answer-Sheet is the last page (both multiple-choice
FORM B
PHYS 272 Spring 2010 EXAM-I There are two parts to the Exam: seven multiple-choice problems (70 points) and one comprehensive problem to be hand-graded (30 points). All pages are double-sided. The Answer-Sheet is the last page (both multiple-choice
Physics 272H Electric and Magnetic Interactions Spring 2011 Physics 272H is the second course of a two-semester sequence of calculus-based physics courses for engineering and science students. It deals with electric and magnetic interactions, which are ce
Fi Final exam: Thursday, May 5, 7-9 PM May PM LILY 3118 Covers all chapters: 14-25. Somewhat more emphasis on Chap. 22-25. All All multiple choice problems.
1
Online course evaluations began Monday, April 18. April 18.
2
Stability of Atoms
Circular motio
Recap: Inductance
emfbat emf R
emf d mag dt
emfcoil dI R dt
2
0 N 2
d
Increasing I increasing B
emf ind
dI L dt R emfind
emfbat
L inductance, or self-inductance 0 N 2 2 L R d Unit of inductance L: Henry = Volt.second/Ampere 1 Inductance resists changes in
Question
Two metal rings lie side-by-side on a table. Current in the left ring runs counterclockwise and is increasing with time. This induces a current in the right ring. This current runs Thi A) Clockwise B) Counterclockwise when viewed from above viewe
Chapter 19
A Microscopic View of Electric Circuits El Ci
1
Current in a Circuit
A microscopic view of electric circuits: Are charges used up in a circuit? How is it possible to create and maintain a nonzero electric it field inside a wire? What is the rol
Magnetic Dipole Moment
0 2R 2 I far from coil: Bz from coil: 4 z 3 0 2 Bz 4 z 3 magnetic dipole moment: R 2 I AI
1 2p far from dipole: E z from dipole: 4 0 z 3 p sq
- vector in the direction of B
1
Magnetic Monopoles
An electric dipole consists of two op
Mean S. D. N
37.67 16.68 43
14.58 7.64 43
1
Electron Current
m electrons 2 n A m v t s nAv t electrons 3 s m
mobile electron density
wire Cross sectional area
Average drift speed speed
Electron current: i
# electrons electrons nAv t
2
Typical Mobile Elec
FORM A
PHYS 272H Spring 2011 EXAM-II There are two parts to the Exam: seven multiple-choice problems (70 points) and one comprehensive problem to be hand-graded (30 points). The Answer-Sheet is the last page (both multiple-choice and hand-graded). Tear of
Potential at a Certain Location
1. Add up the contribution of all point charges at this point q2 r2 r1 A
1 qi VA = i 4 0 ri
q1
2. Travel along a path from point very far away to the location of interest and add up E dl at each step:
dl E
VA = E dl
A
q2
Electric Field and Potential
Definitions:
! ! Electric field is the negative gradient of potential: E = ! gradV = !"V
!V !V !V Ey = " Ex = " Ez = " !y !x !z i Potential Difference: f dl ! f ! #U = "Wint = " ! F dl V " V = " E dl f F f i !i ! !i #V = " ! E
Potential Energy
Introduced the concept of electric field E to deal with forces Introduced electric potential V to deal with work and energy Electric potential: electric potential energy per unit charge Potential energy is associated with pairs of interac
Uniformly Charged Rod
At distance r from midpoint along a line perpendicular to the rod:
! Ey = 0 =
& Q 1# % (r 4!" 0 % r r 2 + ( L / 2 )2 ( $ '
For very long rod:
! E=
1 # 2 (Q / L ) & % (r ' r 4!" 0 $
Field at the ends: Numerical calculation
Uniformly C
Chapter 15
Electric Field of Distributed Charges
Distributed Charges
!( x ', y ', z ')
! E ( x, y, z ) =
Qi 1 # r 2 ri 4!" 0 i =1 i
N
( x ', y ', z ')
( x, y, z )
! E ( x, y, z ) =
1 4!" 0
#( x ', y ', z ')rdx ' dy ' dz ' 2 $ r
Uniformly Charged Thin Rod
Conductors and Insulators
Different materials respond differently to electric field Conductor: contains mobile charges that can move through material Insulator: contains no mobile charges Conductor
Mobile charges Polarization Static equilibrium Excess cha