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(PHYS2421)[2012](f)midterm~=vfemuek^_21420.pdf
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PHYS 2421 Fundamentals of Physics
Fall 2012
Midterm Examination : Solution
2:15 C 4:00 pm, LTD, 27 Oct 2012
Problem
#
Total Points
Your
Points
1
6
2
15
3
7
4
17
5
25
6
20
7
10
Total
100
Name: _____________________________
Student ID: ________________________
Tutorial Section No.: . T1 . T2 . T3 . T4
Important:
1. There are 7 problems in this exam paper. Answer ALL problems.
2. The examination papers are single-sided. Please write your answers and solutions only on the front pages of the examination papers labeled with page numbers. The back side of the pages is for your drafts.
3. This is a close book examination. You are not allowed to bring any book or paper to the examination room. An electronic calculator is allowed.
4. Please make your student ID available for checking.
5. Please turn off all paging and telecommunication devices. You will be deducted 10 points if your device beeps or vibrates. You will be disqualified if you use your device any time during the course of the examination.
6. You can find a list of formulae in the next page. Note that not every one of them is needed to answer this exam paper.
7. Anyone caught cheating in this exam will fail this course.
Buena Suerte / Viel Glck / Bonne Chance / Good Luck / \
Formulae
NOTE: not every formula listed here is needed in answering this exam paper.
C2 m2 N-1, Coulombs Law , 12010854.8....
221041rqqF...
2041rqE...
Electric field due to a charge ring 2/3220)(4RzqzE....
Electric field due to a charge disk ...........22012RzzE..
Electric field just on and above the conductor surface (vacuum) 0...E
An electric dipole in an electric field , Ep......
EpU.....
Gauss law and totalqAdE.....0.
freeqAdE.......0
Electric potential due to a point charge where we define . rqV041...
0)(..V
Potential difference .........baabbaabsdEsdEVVV....
Capacitance , A parallel plate capacitor VQC.
dAC0...
A cylindrical capacitor, A spherical capacitor )/ln(/20abLC...
)/(40ababC....
Energy stored in a capacitor 221CVU.
Energy density in an electric field 2021Eu..
For a sphere of radius R, volume is , surface area is 334R.
24R.
As . , 1||..x
2/11/1xx...
2/11xx...
Magnetic force on a charge: , on a current wire BvqF.....
BLiF.....
Magnetic dipole in a magnetic field , ANi....
B.......
BU......
Magnetic field generated by a current carrying wire: 02sin4idsdBr....
Magnetic field from a long straight wire: with T m/A 02iBR...
70104.....
kabbajabbaiabbabayxyxxzxzzyzy.)(.)(.)(.........
, |sin|||.abba....
zzyyxxbababaabba......cos..
Centripetal force of a circular motion: rmvF2.
Problem 1 [6 Points]
When a dielectric is placed partly into a parallel plate capacitor which