UNIVERSITY OF GAZIANTEP
DEPARTMENT OF ENGINEERING PHYSICS
EP 106 General Physics II
First Midterm Exam Questions
14/07/2005
TIME 90 min.
SUMMER SCHOOL
[1]. Three point charges (q
a
= q
b
=q
c
=1x10
–6
C)
are placed in the straight line at different points
as shown in Figure. If d = 5 cm, determine
(a) the electric force acting on q
c
(b) the magnitude and direction of the electric
field at point A due to these charges
(c) total electrostatic potential at point A due to these charges
(d) the electric potential energy required to remain the charges in the given configuration.
[2]. On a thin rod of length L lying along the x-axis
with one end at the origin (x = 0), as in Figure, there
is distributed a charge per unit length is given by
Ax
=
λ
, where
A
is a constant.
(a) If the total charge on the rod is
Q
, calculate the
constant
A
in terms of
Q
and
L
.
(b) Find an expression for the electric potential at
point
P
(0,
y
).
Hint:
cax
ax
xdx ++=
+
22
22
[3]. Consider a spherical shell of radius 25 cm with a
surface charge density of 60 C/m
2
. A point charge of
10 C is located at the center of the spherical shell.
Using the Gauss’ law, determine the electric field at
(a)
r
= 40 cm, (b)
r
= 25 cm and (c)
r
= 15 cm.
[4].
(a) When two capacitors are connected in parallel, the resulting combination has a total
capacitance 9 F. When the same two capacitors are connected in series, the resulting
combination has a total capacitance 2 F. What are the capacitances of the two
capacitors?
(b) If these two capacitors are connected in parallel to a voltage source which has 12
Volts, what are the accumulated charges and voltage accross on each capacitor?
(c) Repeat part (b), if these two capacitors are connected in series.
Constants
:
e
=1.6x10
-19
C,
k
= 9x10
9
N.m
2
/C
2
,
o
=8.85x10
-12
C
2
/N.m
2
,
o
=4x 10
-7
T.m/A, 1C = 10
-6
C
L
x
y
P
(0
,y
)
λ
d d d
+q
a
–q
b
+q
c
A
+
+
+
+
+
+
+
+
+q
Q
Empty
space
R
