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THE IUG
DATE:27-3-2007
PHYSB 1301
FIRST MID EXAM.
………………………:‫الرقم الجامعي‬
DEPT. OF PHYSICS
TIME:1-Hr
.……… ………………………………………:‫اسم الطـالب‬
Part I
Part II
Q1
Q2
Q3
Total
Q4
PART I: choose the correct answer
1) An insulator is a material
a) containing no electrons
c) through which electrons do not flow easily
b) cannot be charged
d) all of them
2) If e  1.6  10 19 C which of the following is acceptable charge?
a) 210-19 C
b) 110-19 C
c) 0.810-19 C
d) 1 C
3) Two point charges Q and –Q are located along the same line as
shown. Where we can place a third charge q so that the net force on
it is zero.
a) between Q and -Q
b) to the left of Q
c) to the right of -Q
Q
-Q
d) non of these
q
4) Charges Q, -Q , and q are placed at the vertices of an equilateral
triangle as shown. The net electric force on q is
d
-Q
a) up
bdown
c) right
d
d
Q
d) left
5) A uniform electric field of E  2  109 i . The electric force F acting on a charge of -6C exists
in this field is
a) 12  103 i N
b)  12  103 i N
c) 3  103 i N
d)  3  103 i N
6) A proton traveling east enters a region of uniform electric field that points west. The proton will
a) speed up
b) speed down
c) go south
d) go north
7) Choose the incorrect statement concerning the electric field lines
a) field lines may cross
c) field lines are tense where E is large
b) field lines point away from positive charges
d) the direction of E is tangent to field lines
2
8) Two point charges of 2Q and –Q are located as shown. The electric
field will be zero at a point
a) between the two charges only
c) right to –Q only
2Q
-Q
b) left to 2Q only
d) left to 2Q or right to -Q
P
9) A rod of length 2a has a uniform positive charge. The direction of
the electric field at point P shown in the figure is
a
a) up
bdown
c) right
a
d) left
10) A uniform electric field of E  24 i  20 j  16k is penetrating a plane of area 2 m2 and lying in
the y-z plane. The electric flux through the plane is
a) 32 N.m2/C
b) 40 N.m2/C
c) 48 N.m2/C
d) 35 N.m2/C
11) The electric flux throught the curved surface of the cone is
b) ER 2
d) ER 2 H
a) 0
c)  ER
E
2
H
R
12) A thin wire of length L has a uniform Q. Concentric with the wire
is a hollow cylinder of length h. The electric flux through the surface of
the cylinder is
h
L
a) zero
b)
Q
o
c)
QL
h o
d)
Qh
L o
13) A solid sphere has a nonuniform charge density given by   r with r is the distance from the
center of the sphere. The unit of the constant  is
a) C/m4
b) C/m3
c) C/m2
d) C/m
14) A point charge is placed at the center of a spherical shell. The electric flux through the surface
of the shell will be increasedd if
a) the radius of the shell is increased
b) the charge is moved closer to the surface
c) another charge is placed near the outer d) non of them
surface of the shell
3
15) Which of the following is incorrect concerning a conductor in electrostatic equilibrium
a) E inside is zero
c) E on the surface is  to the surface
b) Q inside is zero
d) V inside is zero
16) An electron is accelerated from point A to point B in a uniform electric field E. If the distance
between A and B is d, then V  VB V A is
a) Ed
b) -Ed
c) E/d
d) –E/d
17) Two concentric spherical shells of radii a and b are charged to a total charge
Q. The electric potential on the inner shell is
a
b
a) zero
b) K Q a
c) K Q b
d) K Q r
18) The electric potential at a point P is 8×103 V. The work required to bring a charge of -2C from
 to P is
a) 16 mJ
c) 4 mJ
b) -16 mJ
d) -4 mJ
4
PART II: Solve the following problems
Q1) a small charged ball of mass 5 g is suspended by a 0,5 m long string in a
uniform electric field of 100 N/C as shown. If the ball is in equilibrium
when the string makes a 15o with the vertical, what is the charge on the
ball?
Q2) A thin rod having a uniformly distributed charge q is bent in a
quarter circle of radius R as shown in the figure. Find the electric
potential V at point P, the center of the circle.
15o
E
y
q
R
p
x
5
Q3) A solid conducting sphere of radius a has a charge Q. Concentric
with this sphere is a thin spherical shell of radius b and a net charge Q. Find the electric field at (a  r  b).
Q
-Q
a
b
Q4) Referring to the previous problem, Find the electric potential at a point inside the sphere (r 
a ).