Flux a circular surface of radius 2 m with unit

13. Flux. A circular surface of radius 2 m, with unit normal
vector ˆ n shown in the figure, is immersed in a uniform
electric field of magnitude E = 4 N / C . What is the elec-
tric flux on the circular surface?
A. 8
√
3 π
Nm 2
/
C
B. - 8
√
3 π
Nm 2
/
C
C. 8 π
Nm 2
/
C
D. - 8 π
Nm 2
/
C
14. Spheres. Consider the spherical conductors A, B, and
C that are arranged as shown. The net charges of con-
ductors A and B are +5 Q and - 2 Q respectively. What
is the charge of conductor C so that the outer surface of
conductor A is +4 Q ?
15. Mojo Jojo. Particles A, B, and C with charges q
A
, q
B
, and q
C
, respectively, are arranged
as shown. For the given equipotential lines, which of the following is/are TRUE about the
charged particles?
I. q
A
= q
B
> 0
II. q
A
= q
B
< 0
III. q
C
< 0
A – 6

First Problem Set First Semester, AY 2015–2016 Physics 72
16. Russian Doll. A negatively charged conducting Russian doll consists
of spherical shaped head and base, each with radii of curvatures R
A
and
R
B
respectively. Let V
A
and V
B
be the electric potentials at head and
base respectively. Which of the following is TRUE about the electric
potentials if R
A
< R
B
?
17. 143Work. What is the work done by the electric field on a - 4 . 0 C charge moving opposite
to the direction of a uniform electric field ( 3 . 0
N
/
C
) for a distance of 0 . 10 m ?
A. +1 . 2 J B. +0 . 3 J C. - 0 . 3 J D. - 1 . 2 J
18. GoodbyeLakas. Given the equipotential lines as shown,
which of the following paths will give the least work
done by the electric field on a positively charged par-
ticle?
A – 7

First Problem Set First Semester, AY 2015–2016 Physics 72
19. Move it! Point charges q
1
and q
2
are placed initially at x = a and x = 3 a respectively.
What is the work done by the electric field due to q
2
if q
1
moves to point x = 6 a along the
path shown?
20. Electric Potential. Four identical charges Q are placed at the corners of a square of side
s . What is the potential at the center of the square?
A.
4 kQ
s 2
B.
8 kQ
2
√
2 s
C.
8 kQ
√
2 s
D. zero
21. Calculating Electric Potential. A charge Q is uniformly distributed on a rod of length 2 a .
What is the potential at point P as shown?
1
( b - a ) 2
-
1
( b + a ) 2