SP212-3321/5521
Exam I
February 1, 2016
Question 1: A positively charged rod is brought close to - but does not touch - the
top of an electroscope. In response, the leaves of the electroscope are observed to
repel each other. What can we say about the charges on the the leaves?
/tA) Both leaves are positively charged^
(B) Both leaves are negatively charged.
(C) One leaf is positively charged, the other is negatively charged.
(D) We do not have enough information to determine which of the above is true.
Question 2: A uniform nonconducting spherical shell has a radius of i?=0.15 m and
carries a charge of Q=7.5 ^C. A point charge with g=3.5 nC is located 0.45 m away
from the center of this sphere. What is the magnitude of the electrostatic force acting
on the point charge?
q=3.6 nC
(A) 7.87 N
(B) 5.24 N
(C) 6.56 N
p) 2.62 N
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SP212-3321/5521
February 1, 2016
Exam I
Question 3: Three point charges (+2.0 fiC, +4.0 /iC, and —6.0 iiC) are placed as
shown. What is the magnitude of the net electrostatic force on the +2.0 fiC charge
due to the other two charges?
y
(A) 3.70 N
(B) 7.47 N
4.08 N
1.01 N)
WUVTT
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xlO
-G.O //.C
2.0 fiC
1.50 m
•
0.90 m
X
4.0 ixC
Question 4: Three point charges {qi = —5.0 //C, q2 = —2.0 //C, and
—+2.0 /iC)
are located at the corners of an equilateral triangle. Each side of the triangle is
0.75 m long. What is the magnitude of the net electrostatic force on qi (the -5.0 fiC
charge) due to the other two charges?
gi=—5.0 fiC
iA) 1-60 ^
177 N
(C) 0 N
(D) 3.20 N
/ 60°
XlO
(E) 6.39 N
^
q2——2.0 fiC
93—4"2.0 nC
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SP212-3321/5521
Exam I
February 1, 2016
i;o=200 m/s
>
q=—3.50fiC
£=5000 N/C
Question 5: A point particle with mass m=4.25xl0~'' kg and charge g=—3.50^C has
an initial velocity of uo=(200 m/s)i when it enters a region of space with a uniform
electric field of £=(5000 N/C)fi What is the particle's speed 3.00 s after it entered
this region?
A) 124 m/s
_B) 76.5 ml£)
(UJ 324 m/s
(D) 0.0525 m/s
(E) 6.38 m/s
(F) 20.7 m/s
uo=250 m/s
»
9=+2.50//C
•>
£=2500 N/C
Question 6: A point particle with mass 771=1.25x10"*^ kg and charge g=+2.50/70 has
an initial velocity of uo=(250 m/s)7 when it enters a region of space with a uniform
electric field of £=(2500 N/C)j. What is the particle's speed 4.00 s after it entered
this region?
(A)
(B)
(C)
(D)
450 m/s
150 m/s
50 m/s
0.200 m/s
(s
'(F) 320 m/s
i'°'i,){C^%'>s) i-i^i^/uioss) -. ?;kt °A
f '^-^os . k'^oi'se-i . |M , „
r/VJ?<900-0 * d
r-
r—
^yv Sfjoo'o--(Choose;;(.3 ocs's) =3*2 =j
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2
s'l£ r-"
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t—
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SP212-3321/5521
Exam I
February 1, 2016
A dipole consists of two charges, of +1.25 mC and —1.25 mC, separated by
a distance of 8.00x10"® m. This dipole is placed in an electric field of strength
E=4500 N/C. The dipole is oriented as shown.
—1.25 mC
,0
'\30°
©'
^ £:=450U N/C
150'
+1.25 mC
Question 7: What is the magnitude of the torque acting on the dipole?
(A) 4.50 N-m
(B) 3.90 N-m
-5
(^C) 2.25 N-ifT) xlO
IB) 1.13 [Tm
(E) 1.95 N-m
Question 8: What is the dipole's electrostatic potential energy when it isin this orien-
tation? (Defining U=0 when the dipole moment is perpendicular tothe electric field.)
(A) +2.25 J
fB) -2.25 J
(3C) +3.90^
(E) +1.95 J
(F) -1.95 J
-S
xlO
^O
- oOSI ^"0
00JI7)
^^.O'XOO-Q^ - 1^
4» f^3 J- = a-j --n
=,0S|
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3*^=3,
(ii
I<?SI
^j:>
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©'
P
r
SP212-3321/5521
February 1, 2016
Exam I
Question 9: The dashed circle represents the cross section of a closed spherical Gaus
sian surface. There are three charges inside the surface: —4.0 mC, —2.0 mC, and an
unknown third charge. The net electric flux passing through the Gaussian surface is
+3.39 X 10^ N-m^/C. What is the third charge?
<JA)+9.0
(B) -9.(3 ^
(C) +43.6 mC
(D) -31.6 mC
-4.0 mC\
; -2.0 mC
(E) +3.0 mC
(F) -3.0 mC
9=?
Question 10: Two very large conducting sheets are parallel and separated by a dis
tance that is small in comparison to the size of either sheet. There is a uniform
electric field of B - +5600 i N/C between them What is the surface charge density
on the inside surface of the sheet on the right?
T
£=5600 N/C
(SA) -4.Q6 C/mQ
(B) +4.96 C7m'
(C) -9.91 C/m^
(D) +9.91 C/m^
(E) -1.98 C/m^
(F) +1.98 C/m^
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