FINAL EXAM
PHYS 121
VERSION C
SUMMER
2003
________________________________________________________________________________________________
The exam is closed book and closed notes.
e=1.6x10
19
C
m
e
=9.11x10
31
kg
k = 8.99x10
9
Nm
2
/C
2
k =
1
4
0
πε
ε
0
= 8.85x10
12
C
2
/ Nm
2
;
μ
0
= 1.26x10
6
Tm/A
F = k
q q
r
1
2
2
;
E = k
q
r
1
2
; Area =
π
r
2
F = qE
1 m = 1000 mm
1 m = 100 cm
1 mega (1M )
= 10
6
parallel: C
eq
= C
1
+C
2
+…C
n
∆
U = W = q
∆
V
∆
V =  E
⋅
d
point charge, sphere:
V =
k
r
q
1
charged plane:
V = V
0
 Ex
j = (ne) v
d
j = i/A
E =
ρ
J
ρ

ρ
0
=
ρ
0
α
(T  T
0
)
P = iV
P = i
2
R = V
2
/R
series: R
eq
= R
1
+ R
2
+..R
n
RCcircuit:
charging: Q = Q
0
(1e
t/RC
),
V
C
= V
∞
(1e
t/RC
),
i = i
0
(e
t/RC
),
V
R
= i
0
R (e
t/RC
),
discharging:
Q = Q
0
e
t/RC
,
i = i
0
(e
t/RC
),
V
c
= V
0
(e
t/RC
),
V
R
= i
0
R (e
t/RC
),
F = qvxB
F = iLxB
v = E/B
qvxB = mv
2
/R
τ
=
μ
xB
μ
= NiA
B
straight wire
=
μ
0
I/2
π
R
B
arc
=
μ
0
I
θ
/4
π
R
B
loop
=
μ
0
I/2R
B
sem
=
μ
0
I/4R B
solenoid
=
μ
0
In
μ
0
= 1.26x10
6
Tm/A
Flux:
Φ
=
B
•
A
emf = d
Φ
/dt
emf
selinduced
= Ldi/dt
emf
max
= NAB
ϖ
AC circuit:
emf = E
m
sin
ϖ
t
I = I
m
sin(
ϖ
t
ϕ
)
X
L
=
ϖ
L
X
C
= 1/
ϖ
C
I
m
= V
m
/Z
tan
ϕ
= (X
L
 X
C)
)/R
P
avg
= I
rms
V
rms
cos
ϕ
cos
ϕ
= R/Z
1. Two point charges are arranged as shown.
In which region could a third charge
+2 C be placed so that the net electrostatic force on it is zero?
A)
I only
B)
I and II only
C)
III only
D)
I and III only
E)
II only
A
Q
=
σ
0
2
E
ε
σ
=
r
2
E
0
πε
λ
=
∫
ε
=
=
Φ
0
encl
q
EdA
∫
⋅

=
∆
ds
E
V
2
2
CV
2
1
V
C
C
2
Q
U
=
⋅
=
=
d
A
C
0
ε
=
V
Q
C
=
d
A
C
0
κε
=
1
n
2
1
eq
C
1
...
C
1
C
1
C
:
series

+
+
=
dt
dQ
i
=
A
i
J
=
i
V
R
=
d
V
E
=
d
V
E
=
A
L
R
ρ
=
1
n
2
1
eq
R
1
...
R
1
R
1
R
:
parallel

+
+
=
2
V
V
max
rms
=
2
I
I
max
rms
=
2
C
L
2
)
X
X
(
R
Z

+
=
LC
1
0
=
ϖ
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View Full Document2. A 5nC charge is placed at the origin, a 6 nC charge is placed 0.3 m from the origin on the x
axis, and a third 3nC charge is placed 0.1 m from the origin on the y axis. The magnitude of the
force on the charge at the origin is
A. 0.13x10
6
N
B. 0.34x10
6
N
C. 5.68x10
6
N
D. 8.90x10
6
N
E.
13.8x10
6
N
3. A spherical conducting shell has charge q=6pC.
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 Spring '08
 Opyrchal
 Magnetic Field, A., BARC, Bsem, emfmax

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