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Unformatted text preview: PH 132 Exam 1 Spring 2005 Student Name __ we 7‘} {53’ 5‘33 g Student Number in
Labeecitation Section Number  (11,...,34) Instructions: 1. Fill out all of the information requested above. Write your name on each page.
2. Clearly'indicate your ﬁnal answers for all multiplechoice questions in the space provided. 3. Present neat and orderly solutions to each problem. Clearly indicate your method of solution
by including equations used for each part. Final answors should be circled or boxed. 4. Be sure to include appropriate units with all answers. 5. The magnitude ofthe electric ﬁeld at a distance 1‘ above the midpoint ofa ﬁnite line of total
charge + q and length L is:
2kg YO? +4r2)% E: Multiple Choice
Problem 1 Problem 2 Total Multiple Choice (2 pts. each) 1) 2) 3) 4) Two point charges gI(positive) and g2 (negative) are separated by a distance d. A third point charge Q (negative) is located a distance (1/2 to the left of the first charge, as shown. l f the net electrostatic force on the third charge is zero, then the magnitudes of the first two
charges must be related according to: A) 92 2 29‘}: \k B) q :39? , ——— :: .__..._....... c) q: = 4931, \ (5%): A D
nswer_m_____w D) 92:997y 5:51 A positiver charged ball is brought close to (but does not touch) the left side of a neutral isolated
conducting Sphere. The conducting sphere is then grounded on the right side while the ball is kept
close. The ground connection is removed and the ball is taken away, leaving the conducting sphere: £9 Answer A) Positively charged via the process of conduction;
B) Negatively charged via the process of conduction;
C) Positively charged via the process of induction;
D) Negatively charged via the process of induction. Consider the electrical; effect ofa dipole at a distance that is large compared with the size ofthe dipole. If you double this distance from the dipole, the strength of the electric ﬁeld is reduced by a factor of:  l
A) 1:2; ‘5“ r3
C) 1E6; *'
D) U8. Answer b Consider the finite line of positive charge q and length L on the cover page. The magnitude of
2kg r052 +4r2y/2 Rcspectively, the magnitude of E in the near ﬁeld (at distances close to the line) and in thefar
ﬁeld (at distances far from the line) is proportional to: the electric field at any distance 1‘ above the midpoint is given by: E = z 2.. '2 ...— H k1:
‘lr’ :2; r «PA: “a: — l
A) L and M L + q kw”...
r r I 1 z 7. 3’ zJai if" I ‘3‘
B ~— d——, wwLIHF’A'LAV a: '5 ‘
) r an r2 FA); (F?) L.) E m4 C) l; and 1~;
r r
D) if and Answermem
r r 5) Consider a ﬁnite nonc‘onducting rod with uniformly distributed positive charge (+Q) along the
positive yards and uniformly distributed negative charge (Q) along the negative yaxis. Each
piece ofthe road has the same length. What is the direction ofthe electric ﬁeld at point P? ® A) positive x direction;
B) negative x direction; C) positive y direction; D
D) negative y direction. Answer_ 6) A point charge (+10q) is iocated at the Center of the flat face of a hemiSphere of radius R.
What is the net electric ﬂux through the curved surface of this hemisphere? A) i;
60 B) 3'1;
80 C) 192;
80 n
J 7) A negative point charge (q) is placed at a distance d away from the inside wall of a thin spherical shell of positive charge (+Q) and radius R. The magnitude of the force acting on
the point charge is equal to: E) km—(fn—QEfu. AHSWer" Z S 8) A 2.0 g particle carrying a charge of 2.0 ,uC is released from rest in a uniform electric ﬁeld
of strength 500 MC. How far will this particle travel in 4.0 5?
‘u—.____‘be nub A) 2.0 m; «ﬁn E
B) 4.0m; C) 8.0 m;
D) 16 m. Answer 9) The ﬁgure below shows two large, parallel, nonconducting sheets with identical (positive)
uniform surface charge densities, and a positive point charge. You move the point charge to each of the four positions shown. Rank the positions according to the magnitude of the net
force experienced by the charge, greatest ﬁrst? “:3 c“ I;
i: genwfi' ‘ 250 :5 " 0‘ 1‘ mate7’ 41‘ "‘ "25. gun—HI
"ﬂ 2* . u a 5: 0
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A) 1 and 2 are tied, followed by 3, then 4;
B) l and 2 are tied, fol10wed by 4, then 3;
C) 1, 2 and 4 are tied, followed by 3;
D) 3 and 4 are tied, followed by l and 2 (which are tied); E
E) all are the same. Answer 10) A ball of charge —50e'resides at the center ofa hollow spherical metal shell that has a net
charge of ~100e. What is the charge on the Shell’s outer surface? A) +50e;
B) +100e;
C) ~50e;
D) 150e. AnswerL Problem I A thin noncondocting half cylinder of radius R and length L carries a uniformly distributed total charge of ~+~q.
Z 3) Using the expression for the electric ﬁeld of a line of charge (see cover page), ﬁnd an expression for the electric ﬁeld E at the origin (midpoint) for this half cylinder. Your solution must include an illustration documenting your approach with all variables that you use clearly labeled. You should use the line of
charge in the picture above for this purpose. (14 pts.) 1}) Find the force on a positive point charge +q located at the origin. (3 pts.) c) At what location on the z—axis could you locate this positive point charge to make the electric ﬁeld at the
origin vanish? Assume that R = 1.0 m and L = 2.0 m. (3 pts.) §_QNUS: Consider the magnitude of the electric ﬁeld at the origin, if instead this were a quarter cylinder.
What is the coefﬁcient C in the following expression: E 5:. cylinder = CE y: cylinder ‘2 (3 pts.) . M, """"""""""" "”““‘"~._._:_\ “HMI‘M" ?
.— i A a. 2 I . W: EEI = lass—© 0' == = . jam (LLr as )‘éﬂ arm. U235
. . ass.
5" :2 Glue y ammo5. enemaEL awmw’s. Rob
__, __ LidMasha "‘ A; " + SUM '. _ 1L
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a" gun. at (Ltltqkzyé 3154
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3'1 _ LI;
<5 " mg, (sz22}? 6 We WM”. seats é/MJTﬁ of: mTé'éRA‘riom Problem 2
Consider an inﬁnitely long nonconducting solid cylinder of uniform volume charge density + ,0 whose core has been removed. The remaining solid portion ofthe cylinder has an inner radius a. and outer radius b.
Use Gauss’ Law to obtain an expression for the magnitude of the electric ﬁeld E
Em N J,
K "
I"
0 a b
MUTE: AT Fab
Top _ f has?
i a“""2£.< b )
Side View a) ElF in the region I” < a . (5 pts.) b) E” in the region a < r < b. (5 pts.) c) Em in the region r > b. (5 pts.) (1) Plot the magnitude of the electric ﬁeld in the radial direction on the graph given.
Be sure to label the actual magnitude of the field at r :0, a, and b . (5 pts.) BONUS: Consider a case where the core is ﬁlled with a material having a uniformly distributed
negative charge (— p' ). Find ' in terms of _: ifthe electric ﬁeld in the region r > b is zero. (3 pts.) use" A Gsoeemw ‘
mew—e weak or? my“;
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germ EMA ﬂeas; and. 42:11” + gm:
Barr 51b: 3 o n —— 3’§°_m3__u
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This note was uploaded on 11/04/2009 for the course PHYSICS 131 taught by Professor Wick during the Spring '08 term at Clarkson University .
 Spring '08
 wick
 Physics

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