Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
https:/quizlet.com/37065300/evolutionchapter19developmentandevolutionflashcards/
How is a zygote transformed into an adult organism?
Embryos start out as a mass of cells. As development continues,
cells in each part of the embryo begin expressing di
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
What is an evolutionary tree?
A diagram of the relationships of ancestry and descent among a
group of species or populations; in paleontological studies the
ancestors may be known from fossils, whereas in studies of
extant spieces the ancestors may be hyp
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
an increase in the upward magnetic ux at
the loop. This means that the direction of the
change in the magnetic ux is upward. Lenzs
law implies that the loop generates an induced
magnetic eld Bind to o
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
Induced Generator EMF
31:07, calculus, numeric, > 1 min, normal.
014 (part 1 of 2) 10 points
An ac generator consists of eight turns of wire,
each of area 0.09 m2 , and total resistance
of 12 . The lo
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
The magnetic eld pole has a circular cross
sectional radius of 2.5 cm.
m
1. The electric eld is perpendicular to r and
directed clockwise.
B
2. The electric eld is perpendicular to r and
directed coun
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
B d v2
R2
Explanation:
Note: The part of the rod which extends
past the rails does not have a bearing on the
answers.
Lenzs law states that the induced current
appears such that it opposes the change
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
3
Faradays Law for solenoid
I
d
dt
d (BA)
.
= N
dt
E = N
t
0
2
3
2
2
5
2
3
Magnetic eld induced by inner solenoid
B = 0 n I .
keywords:
So the induced emf is
d
dt
d (B A2 )
= N1
dt
dB
= N1 A2
dt
d (0
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
6
keywords:
009 (part 2 of 2) 10 points
What is the acceleration when the velocity
v = 1 m/s?
Correct answer: 0.0381898 m/s2 .
Explanation:
To get the velocity as a function of time we
need the accele
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
change direction. The induced current will
be in a direction to oppose this change; i.e.,
clockwise.
003 (part 2 of 3) 10 points
What is the expression for the magnitude of
the induced current in the
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
keywords:
B = B A
Bar Pulled Through a Field 03
31:02, calculus, multiple choice, > 1 min, normal.
008 (part 1 of 2) 10 points
A bar of negligible resistance and mass of
33 kg in the gure below is pul
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
the current in the straight wire.
Correct answer: 63.2227 mV.
Explanation:
Let : N = 100 ,
= 200 rad/s ,
= 22 cm ,
a = 5.3 cm ,
b = 17 cm , and
I0 = 50 A .
dr
4
which is a maximum when the cosine fun
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
Changing Magnetic Field 03
31:01, calculus, numeric, > 1 min, normal.
001 (part 1 of 1) 10 points
The plane of a rectangular coil of dimension
5 cm by 8 cm is perpendicular to the direction
of a magne
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
038 (part 1 of 3) 10 points
Consider the circuit below.
C
The maximum voltage on the capacitor C
will be given by
max
1. VC
=
S b
E
max
2. VC
=
a
L
max
=
3. VC
R
max
4. VC
=
After leaving the switch a
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
I0 =
T
2. t =
10
T
3. t =
correct
12
T
4. t =
4
T
5. t =
3
T
6. t =
2
T
7. t =
5
3T
8. t =
4
2
9. t =
5
7
10. t =
8
Explanation:
V
.
R
The rms current is
Irms =
=
I2
1
T
T
(I0 sin t)2 dt
0
I0
V
= =
2
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
Uc =
Q2
Q2
= m cos2
2C
2C
t
LC
2. UL =
3. UL =
4. UL =
5. UL =
Q2
m
2C
Q2
m
2C
Q2
m
2C
Q2
m
2C
Q2
m
2C
t
correct
LC
t
exp
LC
sin2
3. U
4. U
5. U
6. U
7. U
1 exp
Q2
t
m
cos
2C
LC
2
Qm
cos2 t L C
=
2
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
Note that when the charge is zero on the
capacitor, the current is at its maximum level.
(Why?) Also
100 H
2 F
5V
19
S b
Qmax = V C ,
a
What is the rst time at which the charge
on the capacitor is zer
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
Explanation:
The magnetic eld of a solenoid is
17
charge Qm on its plates. At t = 0 the switch
is closed.
C
B = 0 n I .
L
The magnetic ux is
Qm
B = B A = (0 n I) (R2 ) ,
S
so by Faradays Law the emf i
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
The magnetic energy within the cylindrical
annulus is
B2
d Um =
Vannulus
2 0
B2
2 r dr
=
2 0
B2
=
r dr
0
16
The permeability of free space is 4
107 T m/A.
Assuming the inner coil is absent, determin
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
8. Ediss
15
This is the same result we got using conservation of energy directly.
dI
= R I0
dt
t=t1
Explanation:
The Simple Way: Once again, we use
the principle of conservation of energy. The
initial
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
11
keywords:
Current Changes
32:02, calculus, numeric, > 1 min, wordingvariable.
019 (part 1 of 2) 10 points
The current in a 90 mH inductor changes with
time as I = b t2 a t.
With a = 6 A/s and b = 1
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
The current is given by
I(t) = I0 et / .
dt
If t = t t1 ,
= 1 and
dt
1 t /
dI
= I0
e
.
dt
Thus for the power transferred from the inductor to the rest of the circuit,
d UM
1
2
= L I0
dt
e2 t /
1
L/R
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Current, I [A]
7.
8.
5
4
3
2
1
0
Current, I [A]
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
5
4
3
2
1
0
while the switch is in the process of being
thrown until the switch is thrown all the way
to position b.
I(t)
0 1 2 3 4 5 6 7 8 910
Time, t
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
5. UL =
6. UL =
7. UL =
8. UL =
9. UL =
10. UL =
Explanation:
After the switch has been closed for a long
time, the current in L does not change any
more, so there is no voltage increase nor decrease across L. Therefore, the current going
E
through L is I
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
What is the power factor for the circuit?
Correct answer: 0.264768 .
Explanation:
The phase angle between the voltage and
the current in the circuit is
= tan1
XL X C
R
cos = cos tan
= cos tan1
Theref
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
keywords:
Power Dissipated as Heat
33:13, trigonometry, numeric, > 1 min, normal.
063 (part 1 of 1) 10 points
An ac power generator produces 50 A rms
at 3600 V. The voltage is stepped up to
100000 V b
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
The current in the RLC circuit reaches a maximum when
1
0 L =
0 C
1
L= 2
0 C
1
=
[2 f ]2 C
1
=
[2 (50500 Hz)]2 (1.5 108 F)
Explanation:
N1
= 13 and
N2
V1,rms = 120 V .
Let :
The voltage is
N2
V1,rms
N
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
Ilight bulb
=
1
0 =
LC
0
=
Since the current is a maximum at resonance, the maximum brightness will occur at
resonance.
keywords:
Max Current in RLC 05
33:07, trigonometry, numeric, > 1 min, normal.
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
23
The inductive reactance is
Vmax
120 V
XL,new =
=
= 80 .
Inew
1.5 A
E
5.
keywords:
Explanation:
The oscillating emf is proportional to
sin(t ). So the right answer is
E
Energy in an Inductor 03
33:0
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
keywords:
RMS Current 02
33:05, trigonometry, numeric, > 1 min, normal.
049 (part 1 of 2) 10 points
A 8 F capacitor is connected to the terminals of a 60 Hz generator whose rms voltage
is 150 V .
Find
Institute for Studies in Theoretical Physics and Mathematics (IPM)
PHY 2180

Fall 2014
Version One Homework 3 Juyang Huang 24018 Mar 02, 2008
T
When t = , where T is the period (equal to
4
1
) of the applied voltage, what is the current
f
in the circuit?
Correct answer: 0.705882 A.
Explanation:
Let : Vmax = 170 V ,
P = 60 W , and
1
T
.
t= =